Difference between drop table and truncate table?

Question

I have some tables that I build as a part of my report rollup. I don't need them afterwards at all. Someone mentioned to truncate them as it would be faster.

Answer 1

DROP TABLE deletes the table.

TRUNCATE TABLE empties it, but leaves its structure for future data.

Answer 2

TRUNCATE TABLE is functionally identical to DELETE statement with no WHERE clause: both remove all rows in the table. But TRUNCATE TABLE is faster and uses fewer system and transaction log resources than 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's data, and only the page deallocations are recorded in the transaction log.

TRUNCATE TABLE removes all rows from a table, but the table structure and its columns, constraints, indexes and so on remain. The counter used by an identity for new rows is reset to the seed for the column. If you want to retain the identity counter, use DELETE instead. If you want to remove table definition and its data, use the DROP TABLE statement.

You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint; instead, use DELETE statement without a WHERE clause. Because TRUNCATE TABLE is not logged, it cannot activate a trigger.

TRUNCATE TABLE may not be used on tables participating in an indexed view.

From http://msdn.microsoft.com/en-us/library/aa260621(SQL.80).aspx

Answer 3

DROP Table

DROP TABLE [table_name];

The DROP command is used to remove a table from the database. It is a DDL command. All the rows, indexes and privileges of the table will also be removed. DROP operation cannot be rolled back.

DELETE Table

DELETE FROM [table_name]
WHERE [condition];

DELETE FROM [table_name];

The DELETE command is a DML command. It can be used to delete all the rows or some rows from the table based on the condition specified in WHERE clause. It is executed using a row lock, each row in the table is locked for deletion. It maintain the transaction log, so it is slower than TRUNCATE. DELETE operations can be rolled back.

TRUNCATE Table

TRUNCATE TABLE [table_name];

The TRUNCATE command removes all rows from a table. It won't log the deletion of each row, instead it logs the deallocation of the data pages of the table, which makes it faster than DELETE. It is executed using a table lock and whole table is locked for remove all records. It is a DDL command. TRUNCATE operations cannot be rolled back.

Answer 4

DELETE TableA instead of TRUNCATE TableA? A common misconception is that they do the same thing. Not so. In fact, there are many differences between the two.

DELETE is a logged operation on a per row basis. This means that the deletion of each row gets logged and physically deleted.

You can DELETE any row that will not violate a constraint, while leaving the foreign key or any other contraint in place.

TRUNCATE is also a logged operation, but in a different way. TRUNCATE logs the deallocation of the data pages in which the data exists. The deallocation of data pages means that your data rows still actually exist in the data pages, but the extents have been marked as empty for reuse. This is what makes TRUNCATE a faster operation to perform over DELETE.

You cannot TRUNCATE a table that has any foreign key constraints. You will have to remove the contraints, TRUNCATE the table, and reapply the contraints.

TRUNCATE will reset any identity columns to the default seed value.

Answer 5

In the SQL standard, DROP table removes the table and the table schema - TRUNCATE removes all rows.

Answer 6

truncate removes all the rows, but not the table itself, it is essentially equivalent to deleting with no where clause, but usually faster.