Help Center/ GaussDB/ Centralized_8.x/ SQL Reference/ SQL Syntax/ D/ DEALLOCATE
Updated on 2024-06-03 GMT+08:00
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DEALLOCATE

Description

DEALLOCATE deallocates prepared statements.

Precautions

  • If you do not explicitly deallocate a prepared statement, it is deallocated when the session ends.
  • The PREPARE keyword in the syntax is always ignored.

Syntax

DEALLOCATE [ PREPARE ] { name | ALL };

Parameters

  • name

    Specifies the name of the prepared statement to be deallocated.

  • ALL

    Deallocates all prepared statements.

Examples

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-- View existing prepared statements.
gaussdb=# SELECT name, statement, parameter_types FROM pg_prepared_statements;
 name | statement | parameter_types 
------+-----------+-----------------
(0 rows)

-- Create four prepared statements q1, q2, q3, and q4.
gaussdb=# PREPARE q1 AS SELECT 1 AS a;
PREPARE
gaussdb=# PREPARE q2 AS SELECT 1 AS a;
PREPARE
gaussdb=# PREPARE q3 AS SELECT 1 AS a;
PREPARE
gaussdb=# PREPARE q4 AS SELECT 1 AS a;
PREPARE

-- View existing prepared statements again.
gaussdb=# SELECT name, statement, parameter_types FROM pg_prepared_statements;
 name |          statement           | parameter_types 
------+------------------------------+-----------------
 q1   | PREPARE q1 AS SELECT 1 AS a; | {}
 q4   | PREPARE q4 AS SELECT 1 AS a; | {}
 q3   | PREPARE q3 AS SELECT 1 AS a; | {}
 q2   | PREPARE q2 AS SELECT 1 AS a; | {}
(4 rows)

-- Delete the prepared statements q4 and view the remaining prepared statements.
gaussdb=# DEALLOCATE q4;
gaussdb=# SELECT name, statement, parameter_types FROM pg_prepared_statements;
 name |          statement           | parameter_types 
------+------------------------------+-----------------
 q1   | PREPARE q1 AS SELECT 1 AS a; | {}
 q3   | PREPARE q3 AS SELECT 1 AS a; | {}
 q2   | PREPARE q2 AS SELECT 1 AS a; | {}
(3 rows)

-- Delete all prepared statements and view the remaining prepared statements.
gaussdb=# DEALLOCATE ALL;
DEALLOCATE ALL
gaussdb=# SELECT name, statement, parameter_types FROM pg_prepared_statements;
 name | statement | parameter_types 
------+-----------+-----------------
(0 rows)
Parent topic: D