13.1.34 TRUNCATE TABLE Statement
TRUNCATE [TABLE] tbl_name
TRUNCATE TABLE is similar to a
DELETE statement that deletes all rows, or a sequence of
DROP TABLE and
CREATE TABLE statements. To achieve high performance, it bypasses the DML method of deleting data. Thus, it cannot be rolled back, it does not cause
ON DELETE triggers to fire, and it cannot be performed for
InnoDB tables with parent-child foreign key relationships.
Truncate operations drop and re-create the table, which is much faster than deleting rows one by one, particularly for large tables.
Truncate operations cause an implicit commit, and so cannot be rolled back. See Section 13.3.3, “Statements That Cause an Implicit Commit”.
Truncation operations cannot be performed if the session holds an active table lock.
TRUNCATE TABLEfails for an
NDBtable if there are any
FOREIGN KEYconstraints from other tables that reference the table. Foreign key constraints between columns of the same table are permitted.
Truncation operations do not return a meaningful value for the number of deleted rows. The usual result is “0 rows affected,” which should be interpreted as “no information.”
As long as the table format file
is valid, the table can be re-created as an empty table with
TRUNCATE TABLE, even if the data or index files have become corrupted.
AUTO_INCREMENTvalue is reset to its start value. This is true even for
InnoDB, which normally do not reuse sequence values.
When used with partitioned tables,
TRUNCATE TABLEpreserves the partitioning; that is, the data and index files are dropped and re-created, while the partition definitions (
.par) file is unaffected.
TRUNCATE TABLEstatement does not invoke
TRUNCATE TABLE is treated for purposes of binary logging and replication as
DROP TABLE followed by
CREATE TABLE—that is, as DDL rather than DML. This is due to the fact that, when using
InnoDB and other transactional storage engines where the transaction isolation level does not permit statement-based logging (
READ COMMITTED or
READ UNCOMMITTED), the statement was not logged and replicated when using
MIXED logging mode. (Bug #36763) However, it is still applied on replication slaves using
InnoDB in the manner described previously.
On a system with a large
InnoDB buffer pool and
TRUNCATE TABLE operations may cause a temporary drop in system performance due to an LRU scan that occurs when removing an
InnoDB table's adaptive hash index entries. The problem was addressed for
DROP TABLE in MySQL 5.5.23 (Bug #13704145, Bug #64284) but remains a known issue for
TRUNCATE TABLE (Bug #68184).
TRUNCATE TABLE can be used with Performance Schema summary tables, but the effect is to reset the summary columns to 0 or
NULL, not to remove rows. See Section 25.12.15, “Performance Schema Summary Tables”.