Syntax
------

TRUNCATE [TABLE] tbl_name
 [WAIT n | NOWAIT]

Description
-----------

TRUNCATE TABLE empties a table completely. It requires the DROP privilege. See
GRANT.

tbl_name can also be specified in the form db_name.tbl_name (see Identifier
Qualifiers).

Logically, TRUNCATE TABLE is equivalent to a DELETE statement that deletes all
rows, but there are practical differences under some circumstances.

TRUNCATE TABLE will fail for an InnoDB table if any FOREIGN KEY constraints
from other tables reference the table, returning the error:

ERROR 1701 (42000): Cannot truncate a table referenced in a foreign key
constraint

Foreign Key constraints between columns in the same table are permitted.

For an InnoDB table, if there are no FOREIGN KEY constraints, InnoDB performs
fast truncation by dropping the original table and creating an empty one with
the same definition, which is much faster than deleting rows one by one. The
AUTO_INCREMENT counter is reset by TRUNCATE TABLE, regardless of whether there
is a FOREIGN KEY constraint.

The count of rows affected by TRUNCATE TABLE is accurate only when it is
mapped to a DELETE statement.

For other storage engines, TRUNCATE TABLE differs from DELETE in the following
ways:

* 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.
* Truncation operations cannot be performed if the session holds an
 active table lock.
* 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 tbl_name.frm 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.
* The table handler does not remember the last
 used AUTO_INCREMENT value, but starts counting
 from the beginning. This is true even for MyISAM and InnoDB, which normally
 do not reuse sequence values.
* When used with partitioned tables, TRUNCATE TABLE preserves
 the partitioning; that is, the data and index files are dropped and
 re-created, while the partition definitions (.par) file is
 unaffected.
* Since truncation of a table does not make any use of DELETE,
 the TRUNCATE statement does not invoke ON DELETE triggers.
* TRUNCATE TABLE will only reset the values in the Performance Schema summary
tables to zero or null, and will not remove the rows.

For the purposes of binary logging and replication, TRUNCATE TABLE is treated
as DROP TABLE followed by CREATE TABLE (DDL rather than DML).

TRUNCATE TABLE does not work on views. Currently, TRUNCATE TABLE drops all
historical records from a system-versioned table.

MariaDB starting with 10.3.0
----------------------------

WAIT/NOWAIT
-----------

Set the lock wait timeout. See WAIT and NOWAIT.

Oracle-mode
-----------

Oracle-mode from MariaDB 10.3 permits the optional keywords REUSE STORAGE or
DROP STORAGE to be used.

TRUNCATE [TABLE] tbl_name [{DROP | REUSE} STORAGE] [WAIT n | NOWAIT]

These have no effect on the operation.

Performance
-----------

TRUNCATE TABLE is faster than DELETE, because it drops and re-creates a table.

With InnoDB, TRUNCATE TABLE is slower if innodb_file_per_table=ON is set (the
default). This is because TRUNCATE TABLE unlinks the underlying tablespace
file, which can be an expensive operation. See MDEV-8069 for more details.

The performance issues with innodb_file_per_table=ON can be exacerbated in
cases where the InnoDB buffer pool is very large and
innodb_adaptive_hash_index=ON is set. In that case, using DROP TABLE followed
by CREATE TABLE instead of TRUNCATE TABLE may perform better. Setting
innodb_adaptive_hash_index=OFF (it defaults to ON before MariaDB 10.5) can
also help. In MariaDB 10.2 only, from MariaDB 10.2.19, this performance can
also be improved by setting innodb_safe_truncate=OFF. See MDEV-9459 for more
details.

Setting innodb_adaptive_hash_index=OFF can also improve TRUNCATE TABLE
performance in general. See MDEV-16796 for more details.

URL: https://mariadb.com/kb/en/truncate-table/