UPDATE - Trigger Functions (Transact-SQL)
Returns a Boolean value that indicates whether an INSERT or UPDATE attempt was made on a specified column of a table or view. UPDATE() is used anywhere inside the body of a Transact-SQL INSERT or UPDATE trigger to test whether the trigger should execute certain actions.
UPDATE ( column )
Is the name of the column to test for either an INSERT or UPDATE action. Because the table name is specified in the ON clause of the trigger, do not include the table name before the column name. The column can be of any data type supported by SQL Server. However, computed columns cannot be used in this context.
UPDATE() returns TRUE regardless of whether an INSERT or UPDATE attempt is successful.
To test for an INSERT or UPDATE action for more than one column, specify a separate UPDATE(column) clause following the first one. Multiple columns can also be tested for INSERT or UPDATE actions by using COLUMNS_UPDATED. This returns a bit pattern that indicates which columns were inserted or updated.
IF UPDATE returns the TRUE value in INSERT actions because the columns have either explicit values or implicit (NULL) values inserted.
The IF UPDATE(column) clause functions the same as an IF, IF...ELSE, or WHILE clause and can use the BEGIN...END block. For more information, see Control-of-Flow Language (Transact-SQL).
UPDATE(column) can be used anywhere inside the body of a Transact-SQL trigger.
If a trigger applies to a column, the
UPDATED value will return as
1, even if the column value remains unchanged. This is by-design, and the trigger should implement business logic that determines if the insert/update/delete operation is permissible or not.
The following example creates a trigger that prints a message to the client when anyone tries to update the
PostalCode columns of the
USE AdventureWorks2012; GO IF EXISTS (SELECT name FROM sys.objects WHERE name = 'reminder' AND type = 'TR') DROP TRIGGER Person.reminder; GO CREATE TRIGGER reminder ON Person.Address AFTER UPDATE AS IF ( UPDATE (StateProvinceID) OR UPDATE (PostalCode) ) BEGIN RAISERROR (50009, 16, 10) END; GO -- Test the trigger. UPDATE Person.Address SET PostalCode = 99999 WHERE PostalCode = '12345'; GO
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