DELETE and TRUNCATE Commands in SQL Server

hi Vipendra,

please refer

http://www.c-sharpcorner.com/Blogs/3379/
http://www.c-sharpcorner.com/blogs/4670/difference-between-truncate-table-and-delete-table.aspx

hope this will help you.

Hi Vipender,

Delete command removes the rows from a table based on the condition that we provide with a WHERE clause. Truncate will actually remove all the rows from a table and there will be no data in the table after we run the truncate command.

TRUNCATE

TRUNCATE is faster and uses fewer system and transaction log resources than DELETE.
TRUNCATE 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 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.You cannot use TRUNCATE TABLE on a table referenced by a FOREIGN KEY constraint.Because TRUNCATE TABLE is not logged, it cannot activate a trigger.
TRUNCATE can not be Rolled back.
TRUNCATE is DDL Command.
TRUNCATE Resets identity of the table.

DELETE

DELETE removes rows one at a time and records an entry in the transaction log for each deleted row.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.
DELETE Can be used with or without a WHERE clause
DELETE Activates Triggers.
DELETE Can be Rolled back.
DELETE is DML Command.
DELETE does not reset identity of the table.



Thanks

Hi vipendra Verma

This is a regular Interview Question for DBA profile.

http://www.sqlserver-training.com/list-10-difference-between-truncate-delete-statement-in-sql-server/-

Thanks :)

Hi,

Refer this link:

http://www.naresh-avari.blogspot.com/2012/07/difference-between-delete-and-truncate.html

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.  This means if you have a table with an identity column and
you have 264 rows with a seed value of 1, your last record will have
the value 264 (assuming you started with value 1) in its identity
columns.  After TRUNCATEing your table, when you insert a new
record into the empty table, the identity column will have a value of
1.  DELETE will not do this.  In the same scenario, if you
DELETEd your rows, when inserting a new row into the empty table, the
identity column will have a value of 265.

Source:http://codebetter.com/raymondlewallen/2005/05/09/the-difference-in-truncate-and-delete-in-sql-server/