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