Contents
Why TRUNCATE is not working?
You have to remove the CONSTRAINT first and then you can make the Truncate. A Truncate is not allowed on a table which referenced by a forign_key. And for example an other difference a Truncate command reserts the IDENTITY columns as well, but a DELETE not.
Why do we TRUNCATE a table?
Typically, TRUNCATE TABLE quickly deletes all records in a table by deallocating the data pages used by the table. This reduces the resource overhead of logging the deletions, as well as the number of locks acquired. Records removed this way cannot be restored in a rollback operation.
Why is TRUNCATE DDL?
TRUNCATE resets the high water mark of the table, effectively eliminating all the previously existing rows. Treating it as a DDL statement allows it to be super-fast, as it allows it to function without retaining undo (rollback) information like DML statements.
Why Delete is DML?
DELETE is a DML command. The DELETE command is used to remove rows from a table based on WHERE condition. It maintains the log, so it slower than TRUNCATE. The DELETE statement removes rows one at a time and records an entry in the transaction log for each deleted row.
What’s the difference between delete table and TRUNCATE TABLE?
Of course, to use the DELETE command you need DELETE permission for that table. TRUNCATE TABLE is similar to DELETE, but this operation is a DDL (Data Definition Language) command. It also deletes records from a table without removing table structure, but it doesn’t use the WHERE clause.
Why does MySQL hang when using TRUNCATE TABLE?
The TRUNCATE may hang, because other processes could use this table, so to check run in shell: Then kill the queries which are using it (change 123 to Id of the process): may also help to investigate any hangs. I faced same issue, and its resolved by restarting mysql server.
How does the truncate function work in InnoDB?
Only with InnoDB table, InnoDB processes TRUNCATE TABLE by deleting rows one by one if there are any FOREIGN KEY constraints that reference the 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.
Do you need permission to use TRUNCATE TABLE?
Of course, you need permission to use TRUNCATE TABLE. In PostgreSQL, you need the privilege TRUNCATE; in SQL Server, the minimum permission is ALTER table; in MySQL, you need the DROP privilege. Finally, Oracle requires the DROP ANY TABLE system privilege to use this command.