Question
There are two main keywords used for deleting data from a table: TRUNCATE and DELETE. Although each achieves the same result, the methods employed for each vastly differ. There are advantages, limitations, and consequences of each that you should consider when deciding which method to use.
Answer
Deleting Data Using TRUNCATE TABLE
TRUNCATE TABLE is a statement that 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; however, it bypasses the transaction log, and the only record of the truncation in the transaction logs is the page deallocation. Records removed by the TRUNCATE TABLE statement cannot be restored. You cannot specify a WHERE clause in a TRUNCATE TABLE statement-it is all or nothing. The advantage to using TRUNCATE TABLE is that in addition to removing all rows from the table it resets the IDENTITY back to the SEED, and the deallocated pages are returned to the system for use in other areas.
In addition, TRUNCATE TABLE statements cannot be used for tables involved in replication or log shipping, since both depend on the transaction log to keep remote databases consistent.
TRUNCATE TABLE cannot be used when a foreign key references the table to be truncated, since TRUNCATE statements do not fire triggers. This could result in inconsistent data because ON DELETE/UPDATE triggers would not fire. If all table rows need to be deleted and there is a foreign key referencing the table, you must drop the index and recreate it. If a TRUNCATE TABLE statement is issued against a table that has foreign key references, the following error is returned:
Deleting Data Using DELETE FROM Statement
DELETE TABLE statements delete rows one at a time, logging each row in the transaction log, as well as maintaining log sequence number (LSN) information. Although this consumes more database resources and locks, these transactions can be rolled back if necessary. You can also specify a WHERE clause to narrow down the rows to be deleted. When you delete a large number of rows using a DELETE FROM statement, the table may hang on to the empty pages requiring manual release using DBCC SHRINKDATABASE (db_name).
When large tables require that all records be deleted and TRUNCATE TABLE cannot be used, the following statements can be used to achieve the same result as TRUNCATE TABLE:
DELETE from "table_name"
DBCC CHECKIDENT("table_name", RESEED, "reseed_value")
I am running this Blog to help other guys, who are looking some bits and pieces in terms of MS technology....
Subscribe to:
Post Comments (Atom)
Split the String values with a special character in MS Flow to convert this into Array
Many times we have a requirement to prepare the Mailing address for some of the documents, suppose there are Address Line1, Address Line2, ...
-
Use the following line of code to Reopen the closed task in CRM 2011 // Re-open the Task to update it SetStateRequest ssr = new SetStat...
-
Use the following line of code to create complete workflow activity with two output parameters. 1) Open Visual Studio 2010 ID. 2) Open ...
-
Sometimes you experienced when you have subgrid in your CRM Form, but when you click the ‘expand’ button to expand the view then it will re...
No comments:
Post a Comment