Numbers of the BIGINT type are within the range from -2 63 to 2 63 - 1, or from -9,,,,,, to 9,,,,,, Starting from Firebird 2. Hex representation for writing to SMALLINT is not explicitly supported but Firebird will transparently convert a hex number to SMALLINT if necessary, provided it falls within the ranges of negative and positive SMALLINT.

The usage and numerical value ranges of hexadecimal notation are described in more detail in the discussion of number constants in the chapter entitled Common Language Elements. The hexadecimal INTEGER s in the above example are automatically cast to BIGINT before being inserted into the table. However, this happens after the numerical value is determined, so 0x 8 digits and 0x 9 digits will be saved as different BIGINT values.

Floating point data types are stored in an IEEE binary format that comprises sign, exponent and mantissa. Precision is dynamic, corresponding to the physical storage format of the value, which is exactly 4 bytes for the FLOAT type and 8 bytes for DOUBLE PRECISION.

Considering the peculiarities of storing floating-point numbers in a database, these data types are not recommended for storing monetary data. For the same reasons, columns with floating-point data are not recommended for use as keys or to have uniqueness constraints applied to them. For testing data in columns with floating-point data types, expressions should check using a range, for instance, BETWEEN , rather than searching for exact matches.

When using these data types in expressions, extreme care is advised regarding the rounding of evaluation results. The FLOAT data type has an approximate precision of 7 digits after the decimal point. To ensure the safety of storage, rely on 6 digits. The DOUBLE PRECISION data type is stored with an approximate precision of 15 digits.

Fixed-point data types ensure the predictability of multiplication and division operations, making them the choice for storing monetary values. Firebird implements two fixed-point data types: NUMERIC and DECIMAL.

According to the standard, both types limit the stored number to the declared scale the number of digits after the decimal point. For instance, NUMERIC 4, 2 defines a number consisting altogether of four digits, including two digits after the decimal point; that is, it can have up to two digits before the point and no more than two digits after the point. If the number 3. The form of declaration for fixed-point data, for instance, NUMERIC p, s , is common to both types.

Understanding the mechanism for storing and retrieving fixed-point data should help to visualise why: for storage, the number is multiplied by 10 s 10 to the power of s , converting it to an integer; when read, the integer is converted back. The method of storing fixed-point data in the DBMS depends on several factors: declared precision, database dialect, declaration type. Further to the explanation above, the DBMS will store NUMERIC data according the declared precision and scale.

Some more examples are:. Always keep in mind that the storage format depends on the precision. For instance, you define the column type as NUMERIC 2,2 presuming that its range of values will be However, the actual range of values for the column will be In storage, the NUMERIC 4,2 , NUMERIC 3,2 and NUMERIC 2,2 data types are the same, in fact. It means that if you really want to store data in a column with the NUMERIC 2,2 data type and limit the range to The storage format in the database for DECIMAL is very similar to NUMERIC , with some differences that are easier to observe with the help of some more examples:.

The DATE , TIME and TIMESTAMP data types are used to work with data containing dates and times. Dialect 3 supports all the three types, while Dialect 1 has only DATE. Dialect 1 DATE data can be defined alternatively as TIMESTAMP and this is recommended for new definitions in Dialect 1 databases. If fractions of seconds are stored in date and time data types, Firebird stores them to ten-thousandths of a second. If a lower granularity is preferred, the fraction can be specified explicitly as thousandths, hundredths or tenths of a second in Dialect 3 databases of ODS 11 or higher.

The time-part of a TIME or TIMESTAMP is a 4-byte WORD, with room for decimilliseconds precision and time values are stored as the number of deci-milliseconds elapsed since midnight. The actual precision of values stored in or read from time stamp functions and variables is:. Functions DATEADD and DATEDIFF support up to milliseconds precision.

Deci-milliseconds can be specified but they are rounded to the nearest integer before any operation is performed. For TIME and TIMESTAMP literals , Firebird happily accepts up to deci-milliseconds precision, but truncates not rounds the time part to the nearest lower or equal millisecond.

Try, for example, SELECT TIME ' Deci-milliseconds precision is rare and is not currently stored in columns or variables. The best assumption to make from all this is that, although Firebird stores TIME and the TIMESTAMP time-part values as the number of deci-milliseconds 10 -4 seconds elapsed since midnight, the actual precision could vary from seconds to milliseconds.

The DATE data type in Dialect 3 stores only date without time. The available range for storing data is from January 01, 1 to December 31, In Dialect 1, date literals without a time part, as well as 'TODAY' , 'YESTERDAY' and 'TOMORROW' automatically get a zero time part.

If, for some reason, it is important to you to store a Dialect 1 timestamp literal with an explicit zero time-part, the engine will accept a literal like ' However, '' would have precisely the same effect, with fewer keystrokes! The TIME data type is available in Dialect 3 only. It stores the time of day within the range from If you need to get the time-part from DATE in Dialect 1, you can use the EXTRACT function. See also the EXTRACT function in the chapter entitled Built-in Functions.

The TIMESTAMP data type is available in Dialect 3 and Dialect 1. It is the same as the DATE type in Dialect 1. The EXTRACT function works equally well with TIMESTAMP as with the Dialect 1 DATE type. The method of storing date and time values makes it possible to involve them as operands in some arithmetic operations. An example is to subtract an earlier date, time or timestamp from a later one, resulting in an interval of time, in days and fractions of days.

DATE increased by n whole days. Broken values are rounded not floored to the nearest integer. TIME increased by n seconds. The fractional part is taken into account. DATE reduced by n whole days. TIME reduced by n seconds. DATEADD , DATEDIFF. For working with character data, Firebird has the fixed-length CHAR and the variable-length VARCHAR data types. The maximum size of text data stored in these data types is 32, bytes for CHAR and 32, bytes for VARCHAR. The maximum number of characters that will fit within these limits depends on the CHARACTER SET being used for the data under consideration.

The collation sequence does not affect this maximum, although it may affect the maximum size of any index that involves the column. If no character set is explicitly specified when defining a character object, the default character set specified when the database was created will be used.

If the database does not have a default character set defined, the field gets the character set NONE. UTF8 comes with collations for many languages.

Non-accented Latin letters occupy 1 byte, Cyrillic letters from the WIN encoding occupy 2 bytes in UTF8 , characters from other encodings may occupy up to 4 bytes. The UTF8 character set implemented in Firebird supports the latest version of the Unicode standard, thus recommending its use for international databases.

While working with strings, it is essential to keep the character set of the client connection in mind. If there is a mismatch between the character sets of the stored data and that of the client connection, the output results for string columns are automatically re-encoded, both when data are sent from the client to the server and when they are sent back from the server to the client. The character set NONE is a special character set in Firebird.

It can be characterized such that each byte is a part of a string, but the string is stored in the system without any clues about what constitutes any character: character encoding, collation, case, etc. are simply unknown. It is the responsibility of the client application to deal with the data and provide the means to interpret the string of bytes in some way that is meaningful to the application and the human user.

Data in OCTETS encoding are treated as bytes that may not actually be interpreted as characters. OCTETS provides a way to store binary data, which could be the results of some Firebird functions. The database engine has no concept of what it is meant to do with a string of bits in OCTETS , other than just store it and retrieve it. Again, the client side is responsible for validating the data, presenting them in formats that are meaningful to the application and its users and handling any exceptions arising from decoding and encoding them.

Each character set has a default collation sequence COLLATE that specifies the collation order. Usually, it provides nothing more than ordering based on the numeric code of the characters and a basic mapping of upper- and lower-case characters. If some behaviour is needed for strings that is not provided by the default collation sequence and a suitable alternative collation is supported for that character set, a COLLATE collation clause can be specified in the column definition.

A COLLATE collation clause can be applied in other contexts besides the column definition. If output needs to be sorted in a special alphabetic sequence, or case-insensitively, and the appropriate collation exists, then a COLLATE clause can be included with the ORDER BY clause when rows are being sorted on a character field and with the GROUP BY clause in case of grouping operations.

For a case-insensitive search, the UPPER function could be used to convert both the search argument and the searched strings to upper-case before attempting a match:. For strings in a character set that has a case-insensitive collation available, you can simply apply the collation, to compare the search argument and the searched strings directly. The following table shows the possible collation sequences for the UTF8 character set.

Collation works according to the position of the character in the table binary. Added in Firebird 2. Collation works according to the UCA algorithm Unicode Collation Algorithm alphabetical. Case-insensitive collation, works without taking character case into account.

Case-insensitive, accent-insensitive collation, works alphabetically without taking character case or accents into account. In Firebird earlier than version 2. Multi-byte character sets and compound indexes limit the size even further.

The maximum length of an indexed string is 9 bytes less than that quarter-page limit. The table below shows the maximum length of an indexed string in characters , according to page size and character set, calculated using this formula.

CREATE DATABASE , Collation sequence , SELECT , WHERE , GROUP BY , ORDER BY. CHAR is a fixed-length data type. If the entered number of characters is less than the declared length, trailing spaces will be added to the field.

Generally, the pad character does not have to be a space: it depends on the character set. For example, the pad character for the OCTETS character set is zero. The full name of this data type is CHARACTER , but there is no requirement to use full names and people rarely do so.

A valid length is from 1 to the maximum number of characters that can be accommodated within 32, bytes. VARCHAR is the basic string type for storing texts of variable length, up to a maximum of 32, bytes. The stored structure is equal to the actual size of the data plus 2 bytes where the length of the data is recorded.

All characters that are sent from the client application to the database are considered meaningful, including the leading and trailing spaces. However, trailing spaces are not stored: they will be restored upon retrieval, up to the recorded length of the string. The full name of this type is CHARACTER VARYING. Another variant of the name is written as CHAR VARYING. In all other respects it is the same as CHAR.

A similar data type is available for the variable-length string type: NATIONAL CHARACTER VARYING. BLOB s Binary Large Objects are complex structures used to store text and binary data of an undefined length, often very large. Specifying the BLOB segment is throwback to times past, when applications for working with BLOB data were written in C Embedded SQL with the help of the gpre pre-compiler. Nowadays, it is effectively irrelevant.

The segment size for BLOB data is determined by the client side and is usually larger than the data page size, in any case. Firebird provides two pre-defined subtypes for storing user data:. The alias for subtype zero is BINARY. This is the subtype to specify when the data are any form of binary file or stream: images, audio, word-processor files, PDFs and so on. Subtype 1 has an alias, TEXT , which can be used in declarations and definitions.

It is a specialized subtype used to store plain text data that is too large to fit into a string type. A CHARACTER SET may be specified, if the field is to store text with a different encoding to that specified for the database.

From Firebird 2. It is also possible to add custom data subtypes, for which the range of enumeration from -1 to , is reserved.

Custom subtypes enumerated with positive numbers are not allowed, as the Firebird engine uses the numbers from 2-upward for some internal subtypes in metadata.

The maximum size of a BLOB field is limited to 4GB, regardless of whether the server is bit or bit. The internal structures related to BLOB s maintain their own 4-byte counters. The following operators are supported completely:. Aggregation clauses work not on the contents of the field itself, but on the BLOB ID.

Aside from that, there are some quirks:. concatenates the same strings if they are adjacent to each other, but does not do it if they are remote from each other. By default, a regular record is created for each BLOB and it is stored on a data page that is allocated for it. If the entire BLOB fits onto this page, it is called a level 0 BLOB. The number of this special record is stored in the table record and occupies 8 bytes. If a BLOB does not fit onto one data page, its contents are put onto separate pages allocated exclusively to it blob pages , while the numbers of these pages are stored into the BLOB record.

This is a level 1 BLOB. If the array of page numbers containing the BLOB data does not fit onto a data page, the array is put on separate blob pages, while the numbers of these pages are put into the BLOB record. This is a level 2 BLOB. FILTER , DECLARE FILTER. The support of arrays in the Firebird DBMS is a departure from the traditional relational model. Supporting arrays in the DBMS could make it easier to solve some data-processing tasks involving large sets of similar data.

Arrays in Firebird are stored in BLOB of a specialized type. Arrays can be one-dimensional and multidimensional and of any data type except BLOB and ARRAY.

This example will create a table with a field of the array type consisting of four integers. The subscripts of this array are from 1 to 4. To specify explicit upper and lower bounds of the subscript values, use the following syntax:. A new dimension is added using a comma in the syntax. In this example we create a table with a two-dimensional array, with the lower bound of subscripts in both dimensions starting from zero:. The DBMS does not offer much in the way of language or tools for working with the contents of arrays.

The database employee. fdb , found in the.. If the features described are enough for your tasks, you might consider using arrays in your projects. Currently, no improvements are planned to enhance support for arrays in Firebird. It is not available as a data type for declaring table fields, PSQL variables or parameter descriptions. It was added to support the use of untyped parameters in expressions involving the IS NULL predicate.

An evaluation problem occurs when optional filters are used to write queries of the following type:. This is a case where the developer writes an SQL query and considers :param1 as though it were a variable that he can refer to twice. The server cannot determine the type of the second parameter since it comes in association with IS NULL. The following example demonstrates its use in practice.

Each named parameter corresponds with two positional parameters in the query. The application passes the parameterized query to the server in the usual positional? in our example. Firebird has no knowledge of their special relation with the first and third parameters: that responsibility lies entirely on the application side. Once the values for size and colour have been set or left unset by the user and the query is about to be executed, each pair of XSQLVAR s must be filled as follows:.

In other words: The value compare parameter is always set as usual. When composing an expression or specifying an operation, the aim should be to use compatible data types for the operands.

When a need arises to use a mixture of data types, it should prompt you to look for a way to convert incompatible operands before subjecting them to the operation. The ability to convert data may well be an issue if you are working with Dialect 1 data.

When you cast to a domain, any constraints declared for it are taken into account, i. If the value does not pass the check, the cast will fail. When operands are cast to the type of a column, the specified column may be from a table or a view. Only the type of the column itself is used.

For character types, the cast includes the character set, but not the collation. The constraints and default values of the source column are not applied.

Keep in mind that partial information loss is possible. For instance, when you cast the TIMESTAMP data type to the DATE data type, the time-part is lost. To cast string data types to the DATE , TIME or TIMESTAMP data types, you need the string argument to be one of the predefined date and time literals see Table 9 or a representation of the date in one of the allowed date-time literal formats:.

It may contain 1 or 2 digits or You can also specify the three-letter shorthand name or the full name of a month in English. A separator, any of permitted characters. Leading and trailing spaces are ignored.

These shorthand expressions are evaluated directly during parsing, as though the statement were already prepared for execution. Thus, even if the query is run several times, the value of, for instance, timestamp 'now' remains the same no matter how much time passes.

If you need the time to be evaluated at each execution, use the full CAST syntax. An example of using such an expression in a trigger:. In Dialect 1, in many expressions, one type is implicitly cast to another without the need to use the CAST function.

For instance, the following statement in Dialect 1 is valid:. In Dialect 1, mixing integer data and numeric strings is usually possible because the parser will try to cast the string implicitly. For example,. In Dialect 3, an expression like this will raise an error, so you will need to write it as a CAST expression:. When multiple data elements are being concatenated, all non-string data will undergo implicit conversion to string, if possible.

Creating a domain does not truly create a new data type, of course. If several tables need columns defined with identical or nearly identical attributes, a domain makes sense. Domain usage is not limited to column definitions for tables and views.

Domains can be used to declare input and output parameters and variables in PSQL code. A domain definition contains required and optional attributes. The data type is a required attribute. Optional attributes include:. Explicit Data Type Conversion for the description of differences in the data conversion mechanism when domains are specified for the TYPE OF and TYPE OF COLUMN modifiers. While defining a column using a domain, it is possible to override some of the attributes inherited from the domain.

Table 3. To add new conditions to the check, you can use the corresponding CHECK clauses in the CREATE and ALTER statements at the table level. Often it is better to leave domain nullable in its definition and decide whether to make it NOT NULL when using the domain to define columns. CREATE DOMAIN in the Data Definition Language DDL section.

To change the attributes of a domain, use the DDL statement ALTER DOMAIN. With this statement you can:. If you change domains in haste, without carefully checking them, your code may stop working! When you convert data types in a domain, you must not perform any conversions that may result in data loss.

Also, for example, if you convert VARCHAR to INTEGER , check carefully that all data using this domain can be successfully converted. ALTER DOMAIN in the Data Definition Language DDL section. The DDL statement DROP DOMAIN deletes a domain from the database, provided it is not in use by any other database objects. DROP DOMAIN in the Data Definition Language DDL section.

SQL expressions provide formal methods for evaluating, transforming and comparing values. SQL expressions may include table columns, variables, constants, literals, various statements and predicates and also other expressions. The complete list of possible tokens in expressions follows. Identifier of a column from a specified table used in evaluations or as a search condition. A column of the array type cannot be an element in an expression except when used with the IS [NOT] NULL predicate.

An expression may contain a reference to an array member i. The reserved words NOT , AND and OR , used to combine simple search conditions in order to create complex assertions. Predicates used to check the existence of values in a set. The IN predicate can be used both with sets of comma-separated constants and with subqueries that return a single column. The EXISTS , SINGULAR , ALL , ANY and SOME predicates can be used only with subqueries.

An expression, similar to a string literal enclosed in apostrophes, that can be interpreted as a date, time or timestamp value. Date literals can be predefined literals 'TODAY' , 'NOW' , etc. or strings of characters and numerals, such as ' Declared local variable, input or output parameter of a PSQL module stored procedure, trigger, unnamed PSQL block in DSQL.

A member of in an ordered group of one or more unnamed parameters passed to a stored procedure or prepared query. A SELECT statement enclosed in parentheses that returns a single scalar value or, when used in existential predicates, a set of values. Operations inside the parentheses are performed before operations outside them.

When nested parentheses are used, the most deeply nested expressions are evaluated first and then the evaluations move outward through the levels of nesting. Clause applied to CHAR and VARCHAR types to specify the character-set-specific collation sequence to use in string comparisons. Expression for obtaining the next value of a specified generator sequence. A constant is a value that is supplied directly in an SQL statement, not derived from an expression, a parameter, a column reference nor a variable.

It can be a string or a number. The maximum length of a string is 32, bytes; the maximum character count will be determined by the number of bytes used to encode each character.

Double quotes are NOT VALID for quoting strings. SQL reserves a different purpose for them. Care should be taken with the string length if the value is to be written to a VARCHAR column. The maximum length for a VARCHAR is 32, bytes. The character set of a string constant is assumed to be the same as the character set of its destined storage.

Each pair of hex digits defines one byte in the string. Strings entered this way will have character set OCTETS by default, but the introducer syntax can be used to force a string to be interpreted as another character set. The client interface determines how binary strings are displayed to the user. The isql utility, for example, uses upper case letters A-F, while FlameRobin uses lower case letters. Other client programs may use other conventions, such as displaying spaces between the byte pairs: '4E 65 72 76 65 6E'.

The hexadecimal notation allows any byte value including 00 to be inserted at any position in the string. However, if you want to coerce it to anything other than OCTETS, it is your responsibility to supply the bytes in a sequence that is valid for the target character set. This is known as introducer syntax. Its purpose is to inform the engine about how to interpret and store the incoming string.

In SQL, for numbers in the standard decimal notation, the decimal point is always represented by period. Inclusion of commas, blanks, etc. will cause errors. Exponential notation is supported. For example, 0. Hexadecimal notation is supported by Firebird 2. Numbers with hex digits will be interpreted as type INTEGER ; numbers with hex digits as type BIGINT.

Hex numbers in the range To coerce a number to BIGINT , prepend enough zeroes to bring the total number of hex digits to nine or above. That changes the type but not the value. When written with eight hex digits, as in 0x9E44F9A8 , a value is interpreted as bit INTEGER. Since the leftmost bit sign bit is set, it maps to the negative range With one or more zeroes prepended, as in 0x09E44F9A8 , a value is interpreted as bit BIGINT in the range The sign bit is not set now, so they map to the positive range This is something to be aware of.

Hex numbers between FFFF FFFF FFFF FFFF are all negative BIGINT. A SMALLINT cannot be written in hex, strictly speaking, since even 0x1 is evaluated as INTEGER. However, if you write a positive integer within the bit range 0x decimal zero to 0x7FFF decimal it will be converted to SMALLINT transparently. It is possible to write to a negative SMALLINT in hex, using a 4-byte hex number within the range 0xFFFF decimal to 0xFFFFFFFF decimal SQL operators comprise operators for comparing, calculating, evaluating and concatenating values.

SQL Operators are divided into four types. Each operator type has a precedence , a ranking that determines the order in which operators and the values obtained with their help are evaluated in an expression. The higher the precedence of the operator type is, the earlier it will be evaluated. Each operator has its own precedence within its type, that determines the order in which they are evaluated in an expression.

Operators with the same precedence are evaluated from left to right. To force a different evaluation order, operations can be grouped by means of parentheses.

Arithmetic operations are performed after strings are concatenated, but before comparison and logical operations. Comparison operations take place after string concatenation and arithmetic operations, but before logical operations. Character strings can be constants or values obtained from columns or other expressions. Combines two or more predicates, each of which must be true for the entire predicate to be true.

Combines two or more predicates, of which at least one predicate must be true for the entire predicate to be true. NEXT VALUE FOR returns the next value of a sequence. SEQUENCE is an SQL-compliant term for a generator in Firebird and its ancestor, InterBase. A step value of 0 returns the current sequence value. A conditional expression is one that returns different values according to how a certain condition is met.

It is composed by applying a conditional function construct, of which Firebird supports several. This section describes only one conditional expression construct: CASE. All other conditional expressions apply internal functions derived from CASE and are described in Conditional Functions.

The CASE construct returns a single value from a number of possible ones. Two syntactic variants are supported:. The simple CASE , comparable to a case construct in Pascal or a switch in C. When this variant is used, test-expr is compared expr 1, expr 2 etc. If no match is found, defaultresult from the optional ELSE clause is returned. If there are no matches and no ELSE clause, NULL is returned. That is, if test-expr is NULL , it does not match any expr , not even an expression that resolves to NULL.

The returned result does not have to be a literal value: it might be a field or variable name, compound expression or NULL literal. A short form of the simple CASE construct is the DECODE function. The first expression to return TRUE determines the result. If no expressions return TRUE , defaultresult from the optional ELSE clause is returned as the result. If no expressions return TRUE and there is no ELSE clause, the result will be NULL.

As with the simple CASE construct, the result need not be a literal value: it might be a field or variable name, a compound expression, or be NULL. NULL is not a value in SQL, but a state indicating that the value of the element either is unknown or it does not exist. When you use NULL in logical Boolean expressions, the result will depend on the type of the operation and on other participating values.

When you compare a value to NULL , the result will be unknown. NULL means NULL but, in Firebird, the logical result unknown is also represented by NULL. It has already been shown that NOT NULL results in NULL. The interaction is a bit more complicated for the logical AND and logical OR operators:. Up to and including Firebird 2. However, there are logical expressions predicates that can return true, false or unknown.

A subquery is a special form of expression that is actually a query embedded within another query. Subqueries are written in the same way as regular SELECT queries, but they must be enclosed in parentheses.

Subquery expressions can be used in the following ways:. To obtain values or conditions for search predicates the WHERE , HAVING clauses. To produce a set that the enclosing query can select from, as though were a regular table or view. Subqueries like this appear in the FROM clause derived tables or in a Common Table Expression CTE. A subquery can be correlated. A query is correlated when the subquery and the main query are interdependent.

To process each record in the subquery, it is necessary to fetch a record in the main query; i. When subqueries are used to get the values of the output column in the SELECT list, a subquery must return a scalar result.

Subqueries used in search predicates, other than existential and quantified predicates, must return a scalar result; that is, not more than one column from not more than one matching row or aggregation. Although it is reporting a genuine error, the message can be slightly misleading. If P resolves as TRUE, it succeeds.

If it resolves to FALSE or NULL UNKNOWN , it fails. A trap lies here, though: suppose the predicate, P , returns FALSE.

In this case NOT P will return TRUE. On the other hand, if P returns NULL unknown , then NOT P returns NULL as well. In SQL, predicates can appear in CHECK constraints, WHERE and HAVING clauses, CASE expressions, the IIF function and in the ON condition of JOIN clauses.

An assertion is a statement about the data that, like a predicate, can resolve to TRUE, FALSE or NULL. Assertions consist of one or more predicates, possibly negated using NOT and connected by AND and OR operators. Parentheses may be used for grouping predicates and controlling evaluation order.

A predicate may embed other predicates. Evaluation sequence is in the outward direction, i. A comparison predicate consists of two expressions connected with a comparison operator. There are six traditional comparison operators:.

For the complete list of comparison operators with their variant forms, see Comparison Operators. If one of the sides left or right of a comparison predicate has NULL in it, the value of the predicate will be UNKNOWN. The following query will return no data, even if there are printers with no type specified for them, because a predicate that compares NULL with NULL returns NULL :.

On the other hand, ptrtype can be tested for NULL and return a result: it is just that it is not a comparison test:. When CHAR and VARCHAR fields are compared for equality, trailing spaces are ignored in all cases. The BETWEEN predicate tests whether a value falls within a specified range of two values.

NOT BETWEEN tests whether the value does not fall within that range. The operands for BETWEEN predicate are two arguments of compatible data types. The search is inclusive the values represented by both arguments are included in the search. In other words, the BETWEEN predicate could be rewritten:. When BETWEEN is used in the search conditions of DML queries, the Firebird optimizer can use an index on the searched column, if it is available.

The LIKE predicate compares the character-type expression with the pattern defined in the second expression. Case- or accent-sensitivity for the comparison is determined by the collation that is in use. A collation can be specified for either operand, if required. If the tested value matches the pattern, taking into account wildcard symbols, the predicate is TRUE. If the search string contains either of the wildcard symbols, the ESCAPE clause can be used to specify an escape character.

Actually, the LIKE predicate does not use an index. So, if you need to search for the beginning of a string, it is recommended to use the STARTING WITH predicate instead of the LIKE predicate. Search for tables containing the underscore character in their names. The STARTING WITH predicate searches for a string or a string-like type that starts with the characters in its value argument. The search is case-sensitive. When STARTING WITH is used in the search conditions of DML queries, the Firebird optimizer can use an index on the searched column, if it exists.

It can be used for an alphanumeric string-like search on numbers and dates. However, if an accent-sensitive collation is in use then the search will be accent-sensitive.

Search for changes in salaries with the date containing number 84 in this case, it means changes that took place in :. SIMILAR TO matches a string against an SQL regular expression pattern. If any operand is NULL , the result is NULL. Otherwise, the result is TRUE or FALSE. The following syntax defines the SQL regular expression format. It is a complete and correct top-down definition. Feel free to skip it and read the next section, Building Regular Expressions , which uses a bottom-up approach, aimed at the rest of us.

Within regular expressions, most characters represent themselves. The only exceptions are the special characters below:. A regular expression that contains no special or escape characters matches only strings that are identical to itself subject to the collation in use. A bunch of characters enclosed in brackets define a character class.

A character in the string matches a class in the pattern if the character is a member of the class:. Within a class definition, two characters connected by a hyphen define a range. A range comprises the two endpoints and all the characters that lie between them in the active collation.

Ranges can be placed anywhere in the class definition without special delimiters to keep them apart from the other elements. Latin letters a..

z and A.. With an accent-insensitive collation, this class also matches accented forms of these characters. Uppercase Latin letters A.. Also matches lowercase with case-insensitive collation and accented forms with accent-insensitive collation. Lowercase Latin letters a.. Also matches uppercase with case-insensitive collation and accented forms with accent-insensitive collation.

Matches horizontal tab ASCII 9 , linefeed ASCII 10 , vertical tab ASCII 11 , formfeed ASCII 12 , carriage return ASCII 13 and space ASCII Including a predefined class has the same effect as including all its members. Predefined classes are only allowed within class definitions. If you need to match against a predefined class and nothing more, place an extra pair of brackets around it.

If a class definition starts with a caret, everything that follows is excluded from the class. All other characters match:. If the caret is not placed at the start of the sequence, the class contains everything before the caret, except for the elements that also occur after the caret:.

If the braces contain two numbers separated by a comma, the second number not smaller than the first, then the item must be repeated at least the first number and at most the second number of times in order to match:. A match is made when the argument string matches at least one of the terms:. A subexpression is a regular expression in its own right. It can contain all the elements allowed in a regular expression, and can also have quantifiers added to it.

In order to match against a character that is special in regular expressions, that character has to be escaped. There is no default escape character; rather, the user specifies one when needed:. Two operands are considered DISTINCT if they have a different value or if one of them is NULL and the other non-null. They are NOT DISTINCT if they have the same value or if both of them are NULL. Since NULL is not a value, these operators are not comparison operators.

The IS [NOT] NULL predicate tests the assertion that the expression on the left side has a value IS NOT NULL or has no value IS NULL. In Firebird 3. This group of predicates includes those that use subqueries to submit values for all kinds of assertions in search conditions.

Existential predicates are so called because they use various methods to test for the existence or non-existence of some assertion, returning TRUE if the existence or non-existence is confirmed or FALSE otherwise. The EXISTS predicate uses a subquery expression as its argument. It returns TRUE if the subquery result would contain at least one row; otherwise it returns FALSE. NOT EXISTS returns FALSE if the subquery result would contain at least one row; it returns TRUE otherwise.

The IN predicate tests whether the value of the expression on the left side is present in the set of values specified on the right side. The set of values cannot have more than items. The IN predicate can be replaced with the following equivalent forms:. When the IN predicate is used in the search conditions of DML queries, the Firebird optimizer can use an index on the searched column, if a suitable one exists.

Queries specified using the IN predicate with a subquery can be replaced with a similar query using the EXISTS predicate. For instance, the following query:. However, a query using NOT IN with a subquery does not always give the same result as its NOT EXISTS counterpart.

The reason is that EXISTS always returns TRUE or FALSE, whereas IN returns NULL in one of these two cases:. when the test value has no match in the IN list and at least one list element is NULL. It is in only these two cases that IN will return NULL while the corresponding EXISTS predicate will return FALSE 'no matching row found'. But, for the same data, NOT IN will return NULL , while NOT EXISTS will return TRUE , leading to opposite results.

Now, assume that the NY celebrities list is not empty and contains at least one NULL birthday. Then for every citizen who does not share his birthday with a NY celebrity, NOT IN will return NULL , because that is what IN does. The search condition is thereby not satisfied and the citizen will be left out of the SELECT result, which is wrong. non-matches will have a NOT EXISTS result of TRUE and their records will be in the result set. If there is any chance of NULL s being encountered when searching for a non-match, you will want to use NOT EXISTS.

The SINGULAR predicate takes a subquery as its argument and evaluates it as TRUE if the subquery returns exactly one result row; otherwise the predicate is evaluated as FALSE. The subquery may list several output columns since the rows are not returned anyway. They are only tested for singular existence. The SINGULAR predicate can return only two values: TRUE or FALSE. A quantifier is a logical operator that sets the number of objects for which this assertion is true.

It is not a numeric quantity, but a logical one that connects the assertion with the full set of possible objects. Such predicates are based on logical universal and existential quantifiers that are recognised in formal logic. In subquery expressions, quantified predicates make it possible to compare separate values with the results of subqueries; they have the following common form:. When the ALL quantifier is used, the predicate is TRUE if every value returned by the subquery satisfies the condition in the predicate of the main query.

If the subquery returns an empty set, the predicate is TRUE for every left-side value, regardless of the operator. This may appear to be contradictory, because every left-side value will thus be considered both smaller and greater than, both equal to and unequal to, every element of the right-side stream. Nevertheless, it aligns perfectly with formal logic: if the set is empty, the predicate is true 0 times, i.

The quantifiers ANY and SOME are identical in their behaviour. Apparently, both are present in the SQL standard so that they could be used interchangeably in order to improve the readability of operators. When the ANY or the SOME quantifier is used, the predicate is TRUE if any of the values returned by the subquery satisfies the condition in the predicate of the main query.

If the subquery would return no rows at all, the predicate is automatically considered as FALSE. DDL statements are used to create, modify and delete database objects that have been created by users.

When a DDL statement is committed, the metadata for the object are created, changed or deleted. This section describes how to create a database, connect to an existing database, alter the file structure of a database and how to delete one. Optionally includes a port number or service name. Full path and file name including its extension.

The file name must be specified according to the rules of the platform file system being used. Database alias previously created in the aliases. conf file. User name of the owner of the new database. It may consist of up to 31 characters. Password of the user name as the database owner. The maximum length is 31 characters; however only the first 8 characters are considered. Page size for the database, in bytes. Possible values are the default , and Specifies the character set of the connection available to a client connecting after the database is successfully created.

Single quotes are required. The CREATE DATABASE statement creates a new database. You can use CREATE DATABASE or CREATE SCHEMA. They are synonymous. A database may consist of one or several files. The first main file is called the primary file , subsequent files are called secondary file[s].

Nowadays, multi-file databases are considered an anachronism. It made sense to use multi-file databases on old file systems where the size of any file is limited. For instance, you could not create a file larger than 4 GB on FAT The primary file specification is the name of the database file and its extension with the full path to it according to the rules of the OS platform file system being used. The database file must not exist at the moment when the database is being created.

If it does exist, you will get an error message and the database will not be created. If the full path to the database is not specified, the database will be created in one of the system directories. The particular directory depends on the operating system. For this reason, unless you have a strong reason to prefer that situation, always specify the absolute path, when creating either the database or an alias for it.

You can use aliases instead of the full path to the primary database file. If you create a database on a remote server, you should specify the remote server specification. The remote server specification depends on the protocol being used. If you use the Named Pipes protocol to create a database on a Windows server, the primary file specification should look like this:. Clauses for specifying the user name and the password, respectively, of an existing user in the security database security2.

The user specified in the process of creating the database will be its owner. This will be important when considering database and object privileges. Clause for specifying the database page size. This size will be set for the primary file and all secondary files of the database. If you specify the database page size less than 4,, it will be changed automatically to the default page size, 4, Other values not equal to either 4,, 8, or 16, will be changed to the closest smaller supported value.

If the database page size is not specified, it is set to the default value of 4, Clause specifying the maximum size of the primary or secondary database file, in pages. When a database is created, its primary and secondary files will occupy the minimum number of pages necessary to store the system data, regardless of the value specified in the LENGTH clause.

The LENGTH value does not affect the size of the only or last, in a multi-file database file. The file will keep increasing its size automatically when necessary. Clause specifying the character set of the connection available after the database is successfully created. The character set NONE is used by default. Notice that the character set should be enclosed in a pair of apostrophes single quotes. Clause specifying the default character set for creating data structures of string data types.

Character sets are applied to CHAR , VARCHAR and BLOB TEXT data types. It is also possible to specify the default COLLATION for the default character set, making that collation sequence the default for the default character set.

The default will be used for the entire database except where an alternative character set, with or without a specified collation, is used explicitly for a field, domain, variable, cast expression, etc.

Clause that specifies the database page number at which the next secondary database file should start. When the previous file is completely filled with data according to the specified page number, the system will start adding new data to the next database file.

For the detailed description of this clause, see ALTER DATABASE. Databases are created in Dialect 3 by default. For the database to be created in SQL dialect 1, you will need to execute the statement SET SQL DIALECT 1 from script or the client application, e. in isql , before the CREATE DATABASE statement. Creating a database in Windows, located on disk D with a page size of 8, The owner of the database will be the user wizard.

So far, we've already learned that Microsoft privately has a gloomy forecast for the future of cloud gaming opens in new tab , and that the company thinks Sony shouldn't worry so much since, hey, future COD games might be as underwhelming as Vanguard opens in new tab. Who knows what we'll learn next? Sign up to get the best content of the week, and great gaming deals, as picked by the editors. One of Josh's first memories is of playing Quake 2 on the family computer when he was much too young to be doing that, and he's been irreparably game-brained ever since.

His writing has been featured in Vice, Fanbyte, and the Financial Times. He'll play pretty much anything, and has written far too much on everything from visual novels to Assassin's Creed. His most profound loves are for CRPGs, immersive sims, and any game whose ambition outstrips its budget. He thinks you're all far too mean about Deus Ex: Invisible War. Open menu Close menu PC Gamer PC Gamer THE GLOBAL AUTHORITY ON PC GAMES.

opens in new tab opens in new tab opens in new tab opens in new tab opens in new tab opens in new tab. US Edition. News Reviews Hardware Best Of Magazine The Top Forum More PCGaming Show Podcasts Coupons Newsletter SignUp Community Guidelines Affiliate Links Meet the team About PC Gamer.

Popular WoW: Dragonflight Darktide Midnight Suns Holiday gifts Warzone 2. Audio player loading…. PC Gamer Newsletter Sign up to get the best content of the week, and great gaming deals, as picked by the editors.

Text messages may be sent over a cellular network , or may also be sent via an Internet connection. The term originally referred to messages sent using the Short Message Service SMS. It has grown beyond alphanumeric text to include multimedia messages using the Multimedia Messaging Service MMS containing digital images, videos, and sound content, as well as ideograms known as emoji happy faces , sad faces, and other icons , and instant messenger applications usually the term is used when on mobile devices.

Text messages are used for personal, family, business and social purposes. Governmental and non-governmental organizations use text messaging for communication between colleagues. In the s, the sending of short informal messages became an accepted part of many cultures, as happened earlier with emailing.

Like e-mail and voicemail and unlike calls in which the caller hopes to speak directly with the recipient , texting does not require the caller and recipient to both be free at the same moment; this permits communication even between busy individuals.

Text messages can also be used to interact with automated systems, for example, to order products or services from e-commerce websites, or to participate in online contests. Advertisers and service providers use direct text marketing to send messages to mobile users about promotions, payment due dates, and other notifications instead of using postal mail , email , or voicemail.

The service is referred to by different colloquialisms depending on the region. It may simply be referred to as a "text" in North America, the United Kingdom, Australia, New Zealand, and the Philippines, an "SMS" in most of mainland Europe, or an "MMS" or "SMS" in the Middle East, Africa, and Asia. The sender of a text message is commonly referred to as a "texter".

The electrical telegraph systems, developed in the early 19th century, used electrical signals to send text messages. In the late 19th century, the wireless telegraphy was developed using radio waves. In , the German Reichspost Reich postal service introduced the first " telex " service. The University of Hawaii began using radio to send digital information as early as , using ALOHAnet. Sitting at a typewriter at home, Hillebrand typed out random sentences and counted every letter, number, punctuation, and space.

Almost every time, the messages contained fewer than characters, thus giving the basis for the limit one could type via text messaging. It was further developed under the leadership of Kevin Holley and Ian Harris see Short Message Service. This was part of ISDN Integrated Services Digital Network and since GSM is based on this, it made its way to the mobile phone. Messages could be sent and received on ISDN phones, and these can send SMS to any GSM phone.

The possibility of doing something is one thing, implementing it another, but systems existed from that sent SMS messages to mobile phones [ citation needed ] compare ND-NOTIS. SMS messaging was used for the first time on 3 December , [8] at the Three Tuns Public House in Reading, Berkshire [9] when Neil Papworth , a year-old test engineer for Sema Group in the UK [10] now Airwide Solutions , [11] used a personal computer to send the text message " Merry Christmas " via the Vodafone network to the phone of Richard Jarvis, [12] [13] who was at a party in Newbury, Berkshire , which had been organized to celebrate the event.

Modern SMS text messaging is usually messaging from one mobile phone to another. Finnish Radiolinja became the first network to offer a commercial person-to-person SMS text messaging service in When Radiolinja's domestic competitor, Telecom Finland now part of TeliaSonera also launched SMS text messaging in and the two networks offered cross-network SMS functionality, Finland became the first nation where SMS text messaging was offered on a competitive as well as on a commercial basis.

GSM was allowed [ by whom? Hence there is no "development" in the US in mobile messaging service. The GSM in the US had to use a frequency allocated for private communication services PCS — what the ITU frequency régime had blocked for DECT — Digital Enhanced Cordless Telecommunications — feet range picocell, but survived. American Personal Communications APC , the first GSM carrier in America, provided the first text-messaging service in the United States. Sprint Telecommunications Venture, a partnership of Sprint Corp.

and three large cable-TV companies, owned 49 percent of APC. APC operated under the brand name of Sprint Spectrum and launched its service on 15 November , in Washington, D. and in Baltimore, Maryland. Vice President Al Gore in Washington, D. made the initial phone-call to launch the network, calling Mayor Kurt Schmoke in Baltimore. Initial growth of text messaging worldwide was slow, with customers in sending on average only 0.

However, not all text-messaging systems use SMS; some notable alternate implementations of the concept include J-Phone 's SkyMail and NTT Docomo 's Short Mail , both in Japan. Text messaging is most often used between private mobile phone users, as a substitute for voice calls in situations where voice communication is impossible or undesirable e.

Texting is also used to communicate very brief messages, such as informing someone that you will be late or reminding a friend or colleague about a meeting. As with e-mail, informality and brevity have become an accepted part of text messaging. Some text messages such as SMS can also be used for the remote control of home appliances. It is widely used in domotics systems. Some amateurs have also built their own systems to control some of their appliances via SMS.

A Flash SMS is a type [19] of text message that appears directly on the main screen without user interaction and is not automatically stored in the inbox. It can be useful in cases such as an emergency e. Short message services are developing very rapidly throughout the world. SMS is particularly popular in Europe, Asia excluding Japan; see below , United States, Australia, and New Zealand and is also gaining influence in Africa.

Popularity has grown to a sufficient extent that the term texting used as a verb meaning the act of mobile phone users sending short messages back and forth has entered the common lexicon. Young Asians consider SMS as the most popular mobile phone application. It is a very influential and powerful tool in the Philippines, where the average user sends 10—12 text messages a day. The Philippines alone sends on average over 1 billion text messages a day, [24] more than the annual average SMS volume of the countries in Europe, and even China and India.

Similarly, in , text messaging played a primary role in the implication of former Detroit Mayor Kwame Kilpatrick in an SMS sex scandal. In many markets, the service is comparatively cheap.

The service is enormously profitable to the service providers. There are also free SMS services available, which are often sponsored, that allow sending [26] and receiving [27] SMS from a PC connected to the Internet. Users on these plans send on average SMS messages every month. Text messaging has become so popular that advertising agencies and advertisers are now jumping into the text messaging business. Services that provide bulk text message sending are also becoming a popular way for clubs, associations, and advertisers to reach a group of opt-in subscribers quickly.

Research suggests that Internet-based mobile messaging will have grown to equal the popularity of SMS in , with nearly 10 trillion messages being sent through each technology. Research has shown that women are more likely than men to use emoticons in text messages. Of many texting trends, a system known as microblogging has surfaced, which consists of a miniaturized blog, inspired mainly by people's tendency to jot down informal thoughts and post them online.

They consist of websites like Twitter and its Chinese equivalent Weibo 微博. As of , both of these websites were popular. In some countries, text messages can be used to contact emergency services. In the UK, text messages can be used to call emergency services only after registering with the emergency SMS service. This service is primarily aimed at people who, because of disability, are unable to make a voice call. It has recently been promoted as a means for walkers and climbers to call [31] [32] emergency services from areas where a voice call is not possible due to low signal strength.

In the US, there is a move to require both traditional operators and Over-the-top messaging providers to support texting to Since the location of a handset is known, systems can alert everyone in an area that the events have made impossible to pass through e.

an avalanche. A similar system, known as Emergency Alert , is used in Australia to notify the public of impending disasters through both SMS and landline phone calls. These messages can be sent based on either the location of the phone or the address to which the handset is registered.

SMS messages are used in some countries as reminders of medical appointments. A recent study by Sims and colleagues examined the outcomes of 24, outpatient appointments scheduled in mental health services in South-East London. US-based cloud radiology information system vendor AbbaDox includes this in their patient engagement services.

Short codes are special telephone numbers, shorter than full telephone numbers, that can be used to address SMS and MMS messages from mobile phones or fixed phones. There are two types of short codes: dialling and messaging. SMS gateway providers facilitate the SMS traffic between businesses and mobile subscribers, being mainly responsible for carrying mission-critical messages, SMS for enterprises, content delivery and entertainment services involving SMS, e.

Considering SMS messaging performance and cost, as well as the level of text messaging services, SMS gateway providers can be classified as resellers of the text messaging capability of another provider's SMSC or offering the text messaging capability as an operator of their own SMSC with SS7. Many operate text-in services on short codes or mobile number ranges, whereas others use lower-cost geographic text-in numbers.

SMS is widely used for delivering digital content, such as news alerts, financial information, pictures, GIFs, logos and ringtones. Such messages are also known as premium-rated short messages PSMS. Services like 82ASK and Any Question Answered have used the PSMS model to enable rapid response to mobile consumers' questions, using on-call teams of experts and researchers.

In November , amidst complaints about unsolicited charges on bills, major mobile carriers in the US agreed to stop billing for PSMS in 45 states, effectively ending its use in the United States. Outside the United States, premium short messages are increasingly being used for "real-world" services. For example, some vending machines now allow payment by sending a premium-rated short message, so that the cost of the item bought is added to the user's phone bill or subtracted from the user's prepaid credits.

Recently, premium messaging companies have come under fire from consumer groups due to a large number of consumers racking up huge phone bills. A new type of free-premium or hybrid-premium content has emerged with the launch of text-service websites. These sites allow registered users to receive free text messages when items they are interested in go on sale, or when new items are introduced.

An alternative to inbound SMS is based on long numbers international mobile number format, e. Additionally, long numbers are non-premium inbound numbers. The use of text messaging for workplace purposes has grown significantly during the mids decade.

As companies seek competitive advantages, many employees are using new technology, collaborative applications, and real-time messaging such as SMS, instant messaging , and mobile communications to connect with teammates and customers. Some practical uses of text messaging include the use of SMS for confirming delivery or other tasks, for instant communication between a service provider and a client e.

Several universities have implemented a system of texting students and faculties campus alerts. One such example is Penn State. One regulation specifically governing the use of text messaging in financial-services firms engaged in stocks, equities, and securities trading is Regulatory Notice , Supervision of Electronic Communications, December , issued to member firms by the Financial Industry Regulatory Authority FINRA.

In Regulatory Notice , FINRA noted that "electronic communications", "e-mail", and "electronic correspondence" may be used interchangeably and can include such forms of electronic messaging as instant messaging and text messaging.

Mobile Industry Review. A comparison predicate consists of two expressions connected with a comparison operator. Overall, do you approve or disapprove of the way that the California Legislature is handling its job? A COLLATE collation clause can be applied in other contexts besides the column definition. The search is case-sensitive. Nowadays, it is effectively irrelevant.

Categories:

• Binary Options online
• Binary Options
• Forex Brokers
• Forex
• Forex Bitcoin