The UPDATE() Function : Update function « Trigger « SQL Server / T-SQL Tutorial

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SQL Server / T-SQL Tutorial » Trigger » Update function 
22.13.1.The UPDATE() Function
5>
6CREATE TABLE Products (
7>      ProductID int NOT NULL ,
8>      ProductName nvarchar (40NOT NULL ,
9>      SupplierID int NULL ,
10>     CategoryID int NULL ,
11>     QuantityPerUnit nvarchar (20NULL ,
12>     UnitPrice money NULL,
13>     UnitsInStock smallint NULL,
14>     UnitsOnOrder smallint NULL,
15>     ReorderLevel smallint NULL,
16>     Discontinued bit NOT NULL
17)
18> GO
1INSERT Products VALUES(1,'F',15,4,'10 999 g pkgs.',61.5,66,6,6,6)
2INSERT Products VALUES(2,'M',14,4,'24 888 g pkgs.',34.8,74,7,7,7)
3INSERT Products VALUES(3,'R',17,8,'24 777 g jars',17,171,0,5,0)
4INSERT Products VALUES(4,'L',4,7,'5 kg pkg.',10,4,20,5,0)
5INSERT Products VALUES(5,'R',12,1,'24 0.5 l bottles',1.23,445,0,25,0)
6INSERT Products VALUES(6,'L',23,1,'50ml',18,57,1,20,0)
7INSERT Products VALUES(7,'O',12,2,'12 boxes',13,23,0,15,0)
8> go

(rows affected)

(rows affected)

(rows affected)

(rows affected)

(rows affected)

(rows affected)

(rows affected)
1>
2>    create TRIGGER ProductIsRationed
3>       ON Products
4>       FOR UPDATE
5>    AS
6>       IF UPDATE(UnitsInStock)
7>       BEGIN
8>       IF EXISTS
9>          (
10>           SELECT 'True'
11>           FROM Inserted i
12>           JOIN Deleted d
13>              ON i.ProductID = d.ProductID
14>           WHERE (d.UnitsInStock - i.UnitsInStock> d.UnitsInStock / 2
15>              AND d.UnitsInStock - i.UnitsInStock > 0
16>          )
17>       BEGIN
18>          RAISERROR('Cannot reduce stock by more than 50%% at once.',16,1)
19>          ROLLBACK TRAN
20>       END
21>       END
22> GO
1>
2> drop TRIGGER ProductIsRationed;
3> GO
1>
2> drop table Products;
3> GO
22.13.Update function
22.13.1.The UPDATE() Function
22.13.2.Is UPDATing a certain column
22.13.3.Get day from a datetime value
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