SQL Tutorial - TRUNCATE TABLE
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SQL Tutorial - TRUNCATE TABLE - • SQL Tutorial - TRUNCATE TABLE
If you want to to see a tutorial on how to use the DELETE statement in SQL Server, check out this video: • SQL Tutorial - DELETE
If you want to see a tutorial on how to use the INSERT statement in SQL Server, check out this video: • SQL Tutorial - INSERT
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This tutorial will give you an overview of the TRUNCATE statement as well as discussing the differences compared to DELETE and show examples.
TRUNCATE TABLE removes all data from a table but keeps the table definition, DROP TABLE would completely remove the table.
TRUNCATE TABLE resets the current identity value and that is shown in an example in this video, we use IDENT_CURRENT statement to identify the current value then run the statement a second time after the TRUNCATE TABLE to see the difference.
TRUNCATE TABLE is also minimally logged, meaning only data pages that are removed are logged and we are unable to ROLLBACK. DELETE will log each row and can be rolled back.
We also show an example of the differences in performance between TRUNCATE and DELETE, when I run TRUNCATE it executes almost instantly but DELETE takes 46 seconds.
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SQL Statements used in the video:
SELECT IDENT_CURRENT('dbo.CustomersSTG2') AS Current_Identity
TRUNCATE TABLE dbo.CustomersSTG2
INSERT INTO dbo.CustomersSTG2 (FullName, Age)
SELECT
FullName
, Age
FROM dbo.CustomersSTG
DELETE FROM dbo.CustomersSTG2
-- TRUNCATE SYNTAX
TRUNCATE TABLE [schema].[tablename]
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