How do I TRUNCATE a table in PostgreSQL?

TRUNCATE

1. Name. TRUNCATE — empty a table or set of tables.
2. Synopsis. TRUNCATE [ TABLE ] [ ONLY ] name [ * ] [, ] [ RESTART IDENTITY | CONTINUE IDENTITY ] [ CASCADE | RESTRICT ]
3. Description. TRUNCATE quickly removes all rows from a set of tables.
4. Parameters. name.

What does restart identity Cascade do?

mytable RESTART IDENTITY CASCADE; If CASCADE is defined, then the sequences of all affected tables are reset.

What does TRUNCATE Cascade do?

The TRUNCATE TABLE CASCADE command succeeds and recursively truncates all the dependent tables. Notice all rows have been removed from the dependent tables, even those that were not related to rows in their parent table.

What is true about TRUNCATE with foreign-key?

TRUNCATE cannot be used on a table that has foreign-key references from other tables, unless all such tables are also truncated in the same command. Checking validity in such cases would require table scans, and the whole point is not to do one.

Does truncate lock table?

TRUNCATE is a DDL command. TRUNCATE TABLE always locks the table and page. The command removes all the data. TRUNCATE TABLE cannot activate a trigger because the operation does not log individual row deletions.

What is difference between truncate and DELETE?

The DELETE statement removes rows one at a time and records an entry in the transaction log for each deleted row. 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.

What is the difference between truncate and delete?

Unlike the DELETE command, the TRUNCATE command is fast. We cannot rollback the data after using the TRUNCATE command….Difference between DELETE and TRUNCATE.

Does truncate reset the identity?

TRUNCATE TABLE removes all rows from a table, but the table structure and its columns, constraints, indexes, and so on remain. If the table contains an identity column, the counter for that column is reset to the seed value defined for the column. If no seed was defined, the default value 1 is used.

What is difference between TRUNCATE and DELETE?

What is difference between TRUNCATE and TRUNCATE Cascade?

Use this if you want to maintain your table but get rid of all the data in it. TRUNCATE TABLE students -> remove all the data in the STUDENTS table. This can be handy for test databases for example. CASCADE is used when deleting a record or table and basically means ‘and everything attached to it’.

Can we TRUNCATE table with foreign key?

As per mysql documentation, TRUNCATE cannot be used on tables with foreign key relationships. There is no complete alternative AFAIK. Dropping the contraint still does not invoke the ON DELETE and ON UPDATE.

Can we TRUNCATE a table with primary key?

To delete data from a table referenced by a foreign key constraint, you cannot use the TRUNCATE TABLE statement. In this case, you must use the DELETE statement instead. The TRUNCATE TABLE statement does not fire the delete trigger if the table has the triggers associated with it.