Use case untuk trigger INSTEAD OF (DML)

Membangun dan Mengoptimalkan Trigger di SQL Server

Florin Angelescu

Instructor

Penggunaan umum trigger INSTEAD OF

Mencegah operasi terjadi
Mengendalikan pernyataan basis data
Menegakkan integritas data

Trigger yang mencegah perubahan

CREATE TRIGGER PreventProductChanges
ON Products
INSTEAD OF UPDATE
AS
    RAISERROR ('Updates of products are not permitted.
                Contact the database administrator if a change is needed.', 16, 1);

Trigger yang mencegah dan memberi notifikasi

CREATE TRIGGER PreventCustomersRemoval
ON Customers
INSTEAD OF DELETE
AS
    DECLARE @EmailBodyText NVARCHAR(50) =
                       (SELECT 'User "' + ORIGINAL_LOGIN() +
                        '" tried to remove a customer from the database.');

    RAISERROR ('Customer entries are not subject to removal.', 16, 1);

    EXECUTE SendNotification @RecipientEmail = '[email protected]'
                              ,@EmailSubject = 'Suspicious database behavior'
                              ,@EmailBody = @EmailBodyText;

Trigger dengan logika kondisional

CREATE TRIGGER ConfirmStock
ON Orders
INSTEAD OF INSERT
AS
    IF EXISTS (SELECT * FROM Products AS p
               INNER JOIN inserted AS i ON i.Product = p.Product
               WHERE p.Quantity < i.Quantity)
        RAISERROR ('You cannot place orders when there is no product stock.', 16, 1);
    ELSE
        INSERT INTO dbo.Orders (Customer, Product, Quantity, OrderDate, TotalAmount)
        SELECT Customer, Product, Quantity, OrderDate, TotalAmount FROM inserted;

Trigger dengan logika kondisional

Logika kondisional untuk trigger

Ayo berlatih!

Membangun dan Mengoptimalkan Trigger di SQL Server