(mysql.info.gz) TRUNCATE

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 13.1.9 `TRUNCATE' Syntax
 ------------------------
 
      TRUNCATE TABLE TBL_NAME
 
 `TRUNCATE TABLE' empties a table completely.  Logically, this is
 equivalent to a `DELETE' statement that deletes all rows, but there are
 practical differences under some circumstances.
 
 For `InnoDB' before version 5.0.3, `TRUNCATE TABLE' is mapped to
 `DELETE', so there is no difference.  Starting with MySQL/InnoDB-5.0.3,
 fast `TRUNCATE TABLE' is available.  The operation will still be mapped
 to `DELETE' if there are foreign key constraints that reference the
 table.
 
 For other storage engines, `TRUNCATE TABLE' differs from `DELETE FROM'
 in the following ways from MySQL 4.0 and up:
 
    * Truncate operations drop and re-create the table, which is much
      faster than deleting rows one by one.
 
    * Truncate operations are not transaction-safe; you will get an
      error if you have an active transaction or an active table lock.
 
    * The number of deleted rows is not returned.
 
    * As long as the table definition 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 does not reuse sequence
      values.
 
 In MySQL 3.23, `TRUNCATE TABLE' is mapped to `COMMIT; DELETE FROM
 TBL_NAME', so it behaves like `DELETE'.   `DELETE' DELETE.
 
 `TRUNCATE TABLE' is an Oracle SQL extension.  This statement was added
 in MySQL 3.23.28, although from 3.23.28 to 3.23.32, the keyword `TABLE'
 must be omitted.
 

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