Oracle in a Nutshell

Name

TRUNCATE

Synopsis

TRUNCATE 
{ TABLE table_name [{PRESERVE | PURGE} 
| {SNAPSHOT | MATERIALIZED VIEW} LOG] 
| CLUSTER cluster
}
[{DROP | REUSE} STORAGE]

Removes all rows from a table or cluster.

The TRUNCATE statement does not create rollback records, so it cannot be rolled back. This characteristic makes TRUNCATE extremely fast, and it is preferable to DELETE FROM, unless the rollback capability is required. When a table is truncated and the DROP STORAGE clause is specified, only the initial extent of the table is retained; all other storage is deallocated.

Keywords

cluster

Specifies the name of the cluster from which rows are to be removed.

PRESERVE ... LOG

Specifies that existing materialized view or snapshot logs on this table should be preserved when the table is truncated. This option is useful when a table is being reloaded during an Export/TRUNCATE/Import operation, because a fast refresh will not be triggered.

PURGE ... LOG

Specifies that existing snapshot logs on this table should be purged when the table is truncated.

DROP STORAGE

Deallocates storage used by the rows and returns the space to the free space pool. This is the default.

REUSE STORAGE

Retains the space used by the deleted rows. This option is useful if the table or cluster will be reloaded with data.

Common keywords and clauses: table_name.