TRUNCATE TABLE removes all rows from a table, but the table structure and its columns, constraints, indexes, and so on remain. For indexes, the delete operation can leave empty pages behind, although these pages will be deallocated quickly by a background cleanup process. If the delete operation does not use a table lock, the table (heap) will contain many empty pages. For example, empty pages in a heap cannot be deallocated without at least an exclusive (LCK_M_X) table lock. Without exception, zero pages are left in the table.Īfter a DELETE statement is executed, the table can still contain empty pages. TRUNCATE TABLE always locks the table (including a schema (SCH-M) lock) and page but not each row. When the DELETE statement is executed using a row lock, each row in the table is locked for deletion. TRUNCATE TABLE removes the data by deallocating the data pages used to store the table data and records only the page deallocations in the transaction log. The DELETE statement removes rows one at a time and records an entry in the transaction log for each deleted row. RemarksĬompared to the DELETE statement, TRUNCATE TABLE has the following advantages: To truncate a partitioned table, the table and indexes must be aligned (partitioned on the same partition function). can be specified as partition numbers separated by the word TO, for example: WITH (PARTITIONS (6 TO 8)) Provide both ranges and individual partitions, for example: WITH (PARTITIONS (2, 4, 6 TO 8)) Provide the partition numbers for several individual partitions separated by commas, for example: WITH (PARTITIONS (1, 5)) Provide the number of a partition, for example: WITH (PARTITIONS (2)) If the WITH PARTITIONS clause is not provided, the entire table will be truncated. If the table is not partitioned, the WITH PARTITIONS argument will generate an error. Specifies the partitions to truncate or from which all rows are removed. WITH ( PARTITIONS ( ) )Īpplies to: SQL Server ( SQL Server 2016 (13.x) through current version) table_name cannot be the OBJECT_ID() function or a variable. Is the name of the table to truncate or from which all rows are removed. Is the name of the schema to which the table belongs.
Mysql truncate table full#
Mysql truncate table update#
This could result in inconsistent data because ON DELETE/ ON UPDATE triggers would not fire.
TRUNCATE TABLE cannot be used when a foreign key references the table to be truncated, since TRUNCATE TABLE statements do not fire triggers.It is not possible to specify a WHERE clause in a TRUNCATE TABLE statement.Two notable exceptions to this rule are the implementations found in PostgreSQL and Microsoft SQL Server, both of which allow TRUNCATE TABLE statements to be committed or rolled back transactionally. Records removed this way cannot be restored in a rollback operation. This reduces the resource overhead of logging the deletions, as well as the number of locks acquired. Typically, TRUNCATE TABLE quickly deletes all records in a table by deallocating the data pages used by the table.(This may also be the case in MySQL, when using a transactional storage engine.) In the Oracle Database, TRUNCATE is implicitly preceded and followed by a commit operation.The following characteristics distinguish TRUNCATE TABLE from DELETE: The TRUNCATE TABLE mytable statement is logically (though not physically) equivalent to the DELETE FROM mytable statement (without a WHERE clause).
To remove the table definition in addition to its data, use the DROP TABLE statement. It was officially introduced in the SQL:2008 standard, as the optional feature F200, "TRUNCATE TABLE statement". The result of this operation quickly removes all data from a table, typically bypassing a number of integrity enforcing mechanisms. In SQL, the TRUNCATE TABLE statement is a Data Manipulation Language (DML) operation that deletes all rows of a table without causing a triggered action.
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