------------------------ System context variables ------------------------ CURRENT_CONNECTION / CURRENT_TRANSACTION (FB 1.5) ------------------------------------------------- Function: Returns system identifier of the active connection/transaction, i.e. a connection/transaction, in which context the given SQL statement is executed. Author: Dmitry Yemanov <dimitr@firebirdsql.org> Syntax rules: CURRENT_CONNECTION / CURRENT_TRANSACTION Type: INTEGER Scope: DSQL, PSQL Example(s): 1. SELECT CURRENT_CONNECTION FROM RDB$DATABASE; 2. NEW.CONN_ID = CURRENT_TRANSACTION; 3. EXECUTE PROCEDURE P_LOGIN(CURRENT_CONNECTION); Note(s): These values are stored on the database header page, so they will be reset after a database restore. ROW_COUNT (FB 1.5) ------------------ Function: Returns number of rows, affected by the last SQL statement. Author: Dmitry Yemanov <dimitr@firebirdsql.org> Syntax rules: ROW_COUNT Type: INTEGER Scope: PSQL, context of the given procedure/trigger. Example(s): UPDATE TABLE1 SET FIELD1 = 0 WHERE ID = :ID; IF (ROW_COUNT = 0) THEN INSERT INTO TABLE1 (ID, FIELD1) VALUES (:ID, 0); Note(s): 1. It can be used to check whether a SELECT statement returned any rows or not. Also it can be used to exit a fetch loop on an explicit PSQL cursor. 2. ROW_COUNT contains zero after EXECUTE STATEMENT call. That's a design limitation, because dynamic SQL statements are executed as nested requests (i.e. in another context). See also: README.cursors SQLCODE / GDSCODE (FB 1.5) -------------------------- Function: Returns numeric error code for the active exception. Author: Dmitry Yemanov <dimitr@firebirdsql.org> Syntax rules: SQLCODE / GDSCODE Type: INTEGER Scope: PSQL, context of the exception handling block. Example(s): BEGIN ... WHEN SQLCODE -802 DO EXCEPTION E_EXCEPTION_1; WHEN SQLCODE -803 DO EXCEPTION E_EXCEPTION_2; WHEN ANY DO EXECUTE PROCEDURE P_ANY_EXCEPTION(SQLCODE); END Note(s): 1. GDSCODE variable returns a numeric representation of the appropriate Firebird error code. 2. Both SQLCODE and GDSCODE always evaluate to zero outside the exception handling block. 3. If you catch exceptions with 'WHEN SQLCODE' block, then only SQLCODE variable contains the error code inside this block, whilst GDSCODE contains zero. Obviously, this situation is opposite for 'WHEN GDSCODE' block. 4. For 'WHEN ANY' block, the error code is set in SQLCODE variable only. 5. If user-defined exception is thrown, both SQLCODE and GDSCODE variables contain zero, regardless of the exception handling block type. INSERTING / UPDATING / DELETING (FB 1.5) ---------------------------------------- Function: Determines type of row operation being executed. Author: Dmitry Yemanov <dimitr@firebirdsql.org> Syntax rules: INSERTING / UPDATING / DELETING Type: BOOLEAN (emulated via pseudo-expression in FB 1.5) Scope: PSQL, triggers only. Example(s): IF (INSERTING OR DELETING) THEN NEW.ID = GEN_ID(G_GENERATOR_1, 1); See also: README.universal_triggers SQLSTATE (FB 2.5) ----------------- Function: Returns character-encoded state for the active exception. Author: Dmitry Yemanov <dimitr@firebirdsql.org> Syntax rules: SQLSTATE Type: CHAR(5) CHARACTER SET ASCII Scope: PSQL, context of the exception handling block. Example(s): BEGIN ... WHEN SQLSTATE '44000' DO EXCEPTION E_CHECK_VIOLATION; WHEN ANY DO EXECUTE PROCEDURE P_ANY_EXCEPTION(SQLSTATE); END Note(s): 1. SQLSTATE always evaluates to NULL outside the exception handling block. RDB$ERROR (FB 4.0) ------------------ Function: Returns specific context of the active exception. Author: Dmitry Yemanov <dimitr@firebirdsql.org> Syntax rules: RDB$ERROR ( context ) context ::= { GDSCODE | SQLCODE | SQLSTATE | EXCEPTION | MESSAGE } GDSCODE, SQLCODE, SQLSTATE - see above EXCEPTION : VARCHAR(63) CHARACTER SET UTF8 Returns name of the active user-defined exception or NULL if active exception is a system one MESSAGE : VARCHAR(1024) CHARACTER SET UTF8 Returns interpreted text for the active exception Type: Depends on context Scope: PSQL, context of the exception handling block. Example(s): BEGIN ... WHEN ANY DO EXECUTE PROCEDURE P_LOG_EXCEPTION(RDB$ERROR(MESSAGE)); END Note(s): RDB$ERROR always contains NULL outside the exception handling block.