Firebird 2.1 Language Reference Update

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Notes: External functions (UDFs) the engine will pass a NULL argument value unchanged to the function. This leads to a NULL result, which is correct. Without the NULL keyword (your only option in pre-2.0 versions), NULL is passed to the function as an empty string and the result is an empty string as well. For more information about passing NULLs to UDFs, see the note at the end of this book. • Depending on how you declare it (see CSTRING note), this function can accept and return strings of up to 32767 characters. • Before Firebird 2.0, the result type was CHAR(n). • In Firebird 1.5.1 and below, the default declaration used CSTRING(80) instead of CSTRING(255). • In InterBase, substr returned NULL if endpos lay past the end of the string. Tip Library: ib_udf Added in: 1.0 Although the function arguments are slightly different, consider using the internal SQL function SUBSTRING instead, for better compatibility and multi-byte character set support. Changed in: 1.5.2, 2.0 Better alternative: Internal function SUBSTRING() substrlen Description: Returns the substring starting at startpos and having length characters (or less, if the end of the string is reached first). Positions are 1-based. If either startpos or length is smaller than 1, an empty string is returned. This function only works correctly with single-byte characters. Result type: VARCHAR(n) Syntax: substrlen (str, startpos, length) Declaration: DECLARE EXTERNAL FUNCTION substrlen CSTRING(255) NULL, SMALLINT, SMALLINT RETURNS CSTRING(255) FREE_IT ENTRY_POINT 'IB_UDF_substrlen' MODULE_NAME 'ib_udf' The above declaration is from the file ib_udf2.sql. The NULL after the argument is an optional addition that became available in Firebird 2. If the argument is declared with the NULL keyword, the engine will pass a NULL argument value unchanged to the function. This leads to a NULL result, 193
Notes: External functions (UDFs) which is correct. Without the NULL keyword (your only option in pre-2.0 versions), NULL is passed to the function as an empty string and the result is an empty string as well. For more information about passing NULLs to UDFs, see the note at the end of this book. • Depending on how you declare it (see CSTRING note), this function can accept and return strings of up to 32767 characters. • Before Firebird 2.0, the result type was CHAR(n). • In Firebird 1.5.1 and below, the default declaration used CSTRING(80) instead of CSTRING(255). Tip Library: ib_udf Added in: IB Firebird 1.0 has also implemented the internal SQL function SUBSTRING, effectively rendering substrlen obsolete in the same version in which it was introduced. SUBSTRING also supports multi-byte character sets. In new code, use SUBSTRING. Better alternative: Internal function TAN() tan Description: Returns an angle's tangent. The argument must be given in radians. Result type: DOUBLE PRECISION Syntax: tan (angle) Declaration: DECLARE EXTERNAL FUNCTION tan DOUBLE PRECISION RETURNS DOUBLE PRECISION BY VALUE ENTRY_POINT 'IB_UDF_tan' MODULE_NAME 'ib_udf' Library: ib_udf Added in: IB tanh 194
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Firebird 2.1 Language Reference Upd
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Table of Contents 1. Introduction .
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Firebird 2.1 Language Ref. Update F
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Firebird 2.1 Language Ref. Update A
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Firebird 2.1 Language Ref. Update s
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Chapter 1 Introduction Subject matt
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Chapter 2 Reserved words and keywor
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LOCK LOG LOG10 LPAD MATCHED MATCHIN
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Chapter 3 Available in: DSQL, PSQL
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Example: select name, age, case upp
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Data types and subtypes • Partial
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Added in: 1.0, 1.5, 1.5.1, 2.0, 2.1
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Chapter 5 DDL statements The statem
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With a special attribute (case-sens
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DIFFERENCE FILE parameter Added in:
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CREATE DOMAIN Available in: DSQL, E
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Example: DDL statements create exce
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Syntax: Example: ALTER EXTERNAL FUN
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DDL statements -- the following que
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DDL statements PROCEDURE A stored p
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DDL statements Description: Firebir
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DDL statements NOT NULL in variable
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CREATE GENERATOR Available in: DSQL
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Better alternative: DROP SEQUENCE D
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) DDL statements lastname varchar(2
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USING INDEX subclause Available in:
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ALTER COLUMN: SET DEFAULT Available
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UNIQUE constraints now allow NULLs
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Example: DDL statements create trig
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Multi-action triggers Added in: 1.5
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NOT NULL in variable declarations C
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DDL statements Restriction on recre
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DDL statements got a chance to put
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ORDER BY Available in: DSQL, PSQL A
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DML statements ROWS can also be use
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DML statements COLLATE in variable
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The same call in ESQL (with obligat
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DML statements Description: A SELEC
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DML statements Aggregate functions
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Syntax: Example: Notes: ::= DML
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DML statements select d.dept_no, d.
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DML statements FIRST and SKIP are b
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DML statements select strlen(lastna
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DML statements Description: A natur
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DML statements • Only non-negativ
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Example: DML statements plan (MyTab
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UNIONs in subqueries Changed in: 2.
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Restrictions DML statements • The
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DML statements Description: Limits
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Chapter 7 Available in: DSQL Added
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Transaction control statements If t
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Transaction control statements •
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Chapter 8 PSQL statements PSQL - Pr
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PSQL statements • If sql_datatype
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Warning PSQL statements If you chan
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PSQL statements exception ex_bad_ty
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PSQL statements as declare variable
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Examples: PSQL statements thoroughl
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leave; end end c = 0; PSQL statemen
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Changed in: 2.0 Context variables D
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Context variables its execution was
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Context variables Description: OLD
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Chapter 10 Changed in: 2.0 Operator
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UNION as subselect Changed in: 2.0
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Chapter 11 Aggregate functions Aggr
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• If the argument is NULL, NULL i
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Result type: INTEGER or BIGINT Synt
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Result type: INTEGER Syntax: BIT_LE
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Internal functions This gives you c
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Available in: DSQL, PSQL Added in:
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Available in: DSQL, PSQL Added in:
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Example: The equivalent CASE constr
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WEEK Bug alert Internal functions M
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Added in: 2.1 Internal functions De
Page 154 and 155: Internal functions • If x is nega
Page 156 and 157: Examples: Internal functions lpad (
Page 158 and 159: Internal functions This will return
Page 160 and 161: Internal functions overlay ('Goodby
Page 162 and 163: Available in: DSQL, PSQL Added in:
Page 164 and 165: Internal functions Description: Cre
Page 166 and 167: Internal functions reverse ('Was it
Page 168 and 169: Added in: 2.1 Internal functions De
Page 170 and 171: Syntax: SINH (number) Important Int
Page 172 and 173: Available in: DSQL, PSQL Added in:
Page 174 and 175: Notes: Internal functions • If th
Page 176 and 177: Description: Returns the arc cosine
Page 178 and 179: Declaration: External functions (UD
Page 180 and 181: Library: ib_udf Changed in: 1.0, 2.
Page 182 and 183: Better alternative: Internal functi
Page 184 and 185: External functions (UDFs) Descripti
Page 186 and 187: Syntax: cot (angle) Declaration: Ex
Page 188 and 189: Declaration: External functions (UD
Page 190 and 191: Library: ib_udf Added in: IB Change
Page 192 and 193: Changed in: 1.5, 1.5.2, 2.0 Better
Page 194 and 195: External functions (UDFs) DECLARE E
Page 196 and 197: See sright. Library: fbudf Added in
Page 198 and 199: Notes: External functions (UDFs) Fo
Page 200 and 201: Syntax: sign (number) Declaration:
Page 202 and 203: Library: fbudf Added in: 1.0 (Win),
Page 206 and 207: Better alternative: Internal functi
Page 208 and 209: Appendix A: Notes Character set NON
Page 210 and 211: Table A.1. How TPB settings affect
Page 212 and 213: Notes A note on CSTRING parameters
Page 214 and 215: Notes Maximum number of indices in
Page 216 and 217: Document History DDL statements ::
Page 218 and 219: Document History Internal functions
Page 220: Appendix C: License notice The cont
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Firebird 2.1 Language Reference Update

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