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PostgreSQL 7.4.30 Documentation
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TRUNCATE

Name

TRUNCATE -- empty a table

Synopsis

TRUNCATE [ TABLE ] name

Description

TRUNCATE quickly removes all rows from a table. It has the same effect as an unqualified DELETE but since it does not actually scan the table it is faster. This is most useful on large tables.

Parameters

name: The name (optionally schema-qualified) of the table to be truncated.

Notes

Only the owner of a table may TRUNCATE it.

TRUNCATE cannot be used if there are foreign-key references to the table from other tables. Checking validity in such cases would require table scans, and the whole point is not to do one.

TRUNCATE will not run any user-defined ON DELETE triggers that might exist for the table.

Examples

Truncate the table bigtable:

TRUNCATE TABLE bigtable;

Compatibility

There is no TRUNCATE command in the SQL standard.

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Comments

Nov. 18, 2005, 11:40 p.m.

1:Tx - transaction;
2:T1 - begin;
3:T2 - select * from t1; => it returns rows;
4:T1 - truncate t1;
5:T2 - select * from t1; => it waits for commit(like lock table);
6:T1 - insert into t1 values(1);
7:T2 - commit;
just now T1 returns the rows added on line 6.