DB2 Version 9.7 for Linux, UNIX, and Windows

TRUNCATE statement

The TRUNCATE statement deletes all of the rows from a table.

Invocation

This statement can be embedded in an application program or issued through the use of dynamic SQL statements. It is an executable statement that can be dynamically prepared only if DYNAMICRULES run behavior is in effect for the package (SQLSTATE 42509).

Authorization

The privileges held by the authorization ID of the statement must include at least one of the following for the table, and all subtables of a table hierarchy:

DELETE privilege on the table to be truncated
CONTROL privilege on the table to be truncated
DATAACCESS authority

To ignore any DELETE triggers that are defined on the table, the privileges held by the authorization ID of the statement must include at least one of the following for the table, and all subtables of a table hierarchy:

ALTER privilege on the table
CONTROL privilege on the table
DBADM authority

To truncate a table that is protected by a security policy, the privileges held by the authorization ID of the statement must include at least one of the following:

CONTROL privilege on the table
DBADM authority

Syntax


             .-TABLE-.              .-DROP STORAGE--.   
>>-TRUNCATE--+-------+--table-name--+---------------+----------->
                                    '-REUSE STORAGE-'   

   .-IGNORE DELETE TRIGGERS--------.   
>--+-------------------------------+---------------------------->
   '-RESTRICT WHEN DELETE TRIGGERS-'   

   .-CONTINUE IDENTITY-.              
>--+-------------------+--IMMEDIATE----------------------------><

Description

table-name

Identifies the table to be truncated. The name must identify a table that exists at the current server (SQLSTATE 42704), but it cannot be a catalog table (SQLSTATE 42832), a nickname (SQLSTATE 42809), a view, a subtable, a staging table, a system-maintained materialized query table, or a range-clustered table (SQLSTATE 42807).

If table-name is the root table of a table hierarchy, all tables in the table hierarchy will be truncated.

DROP STORAGE or REUSE STORAGE

Specifies whether to drop or reuse the existing storage that is allocated for the table. The default is DROP STORAGE.

DROP STORAGE: All storage allocated for the table is released and made available. If this option is specified (implicitly or explicitly), an on-line backup would be blocked.
REUSE STORAGE: All storage allocated for the table will continue to be allocated for the table, but the storage will be considered empty. This option is only applicable to tables in DMS table spaces and is ignored otherwise.

IGNORE DELETE TRIGGERS or RESTRICT WHEN DELETE TRIGGERS

Specifies what to do when delete triggers are defined on the table. The default is IGNORE DELETE TRIGGERS.

IGNORE DELETE TRIGGERS: Any delete triggers that are defined for the table are not activated by the truncation operation.
RESTRICT WHEN DELETE TRIGGERS: An error is returned if delete triggers are defined on the table (SQLSTATE 428GJ).

CONTINUE IDENTITY

If an identity column exists for the table, the next identity column value generated continues with the next value that would have been generated if the TRUNCATE statement had not been executed.

IMMEDIATE

Specifies that the truncate operation is processed immediately and cannot be undone. The statement must be the first statement in a transaction (SQLSTATE 25001).

The truncated table is immediately available for use in the same unit of work. Although a ROLLBACK statement is allowed to execute after a TRUNCATE statement, the truncate operation is not undone, and the table remains in a truncated state. For example, if another data change operation is done on the table after the TRUNCATE IMMEDIATE statement and then the ROLLBACK statement is executed, the truncate operation will not be undone, but all other data change operations are undone.

Rules

Referential Integrity: The table, and all tables in a table hierarchy, must not be a parent table in an enforced referential constraint (SQLSTATE 428GJ). A self-referencing RI constraint is permitted.
Partitioned tables: The table must not be in set integrity pending state due to being altered to attach a data partition (SQLSTATE 55019). The table needs to be checked for integrity prior to executing the TRUNCATE statement. With DB2® Version 9.7 Fix Pack 1 and later releases, the table must not have any logically detached partitions (SQLSTATE 55057). The asynchronous partition detach task must complete prior to executing the TRUNCATE statement.
Exclusive Access: No other session can have a cursor open on the table, or a lock held on the table (SQLSTATE 25001).
WITH HOLD cursors: The current session cannot have a WITH HOLD cursor open on the table (SQLSTATE 25001).

Notes

Table statistics: The statistics for the table are not changed by the TRUNCATE statement.
Number of rows deleted: SQLERRD(3) in the SQLCA is set to -1 for the truncate operation. The number of rows that were deleted from the table is not returned.

Example

Example 1: Empty an unused inventory table regardless of any existing triggers and return its allocated space.

   TRUNCATE TABLE INVENTORY
     IGNORE DELETE TRIGGERS
     DROP STORAGE
     IMMEDIATE

Example 2: Empty an unused inventory table regardless of any existing delete triggers but preserve its allocated space for later reuse.

   TRUNCATE TABLE INVENTORY
      REUSE STORAGE
      IGNORE DELETE TRIGGERS
      IMMEDIATE