Trunacate And Delete Operation in SqlServer

Hi Michell,


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, its columns,
constraints, indexes and so on, remains. 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 cannot 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 Michell,

Truncate:
1. It is a DDL Command

2. by using Truncate,all rows of a table deleted

TRUNCATE TABLE Table_Name;

3. including all spaces allocated for the records are ALSO removed
4. Its Auto Commited

TRUNCATE TABLE Table_Name;

Delete:
1. It is a DML Command
2. by using Deletete,we have option to delete all rows of a table or by using where clause we can delete particular records.

DELETE FROM Table_Name ;
DELETE FROM Table_Name WHERE ColumnID;

3. the space for the records remain.
4. Need to commit by using Commit Command.

Thanks.

Hi Michell,

Following are the differences:

TRUNCATE is faster than delete cause it does not actually removes the rows, but it deallocates the data pages and pointers. These pages are later overwritten or freed when database is shrunk. TRUNCATE information is also logged by making entries of data pages in the log file. You can use TRUNCATE in transactions also.

DELETE on the other hand logs data for each row getting removed so it is slow and takes more resource to perform the operation. DELETE can also be used in transactions.

IF you have a lot of rows to delete than use TRUNCATE otherwise DELETE, but if you are planning to do some recovery where individual logging of rows is important use DELETE.

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