PREPARE

Description

Creates a prepared statement.

A prepared statement is a performance optimizing object on the server. When the PREPARE statement is executed, the specified query is parsed, analyzed, and rewritten. When EXECUTE is executed, the prepared statement is planned and executed. This avoids repetitive parsing and analysis. After the PREPARE statement is created, it exists throughout the database session. Once it is created (even if in a transaction block), it will not be deleted when a transaction is rolled back. It can only be deleted by explicitly calling DEALLOCATE or automatically deleted when the session ends.

Precautions

The name of a PREPARE statement must be unique.

Syntax

PREPARE name FROM string

Parameters

• name

  Specifies an identifier for the prepared query.

• string

  Specifies a character string, which is a prepared SQL statement. The user variable @var_name is not supported. The following statements are supported:

  • SELECT
  • INSERT
  • UPDATE
  • DELETE

Examples

m_db=# PREPARE p1 FROM 'SELECT 10 < 52';
PREPARE
m_db=# EXECUTE p1;
 ?column? 
----------
 t
(1 row)