c# print barcode labels Triggers in Visual Studio .NET

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4 Triggers
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CREATE TABLE dbo.T1 ( keycol INT NOT NULL PRIMARY KEY, datacol VARCHAR(10) NOT NULL );
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Run the following code to create the trigger trg_T1_i .
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CREATE TRIGGER trg_T1_i ON T1 FOR INSERT AS DECLARE @rc AS INT = (SELECT COUNT(*) FROM (SELECT TOP (2) * FROM inserted) AS D); IF @rc = 0 RETURN; DECLARE @keycol AS INT, @datacol AS VARCHAR(10); IF @rc = 1 -- single row BEGIN SELECT @keycol = keycol, @datacol = datacol FROM inserted; PRINT 'Handling keycol: ' + CAST(@keycol AS VARCHAR(10)) + ', datacol: ' + @datacol; END ELSE -- multi row BEGIN DECLARE @C AS CURSOR; SET @C = CURSOR FAST_FORWARD FOR SELECT keycol, datacol FROM inserted; OPEN @C; FETCH NEXT FROM @C INTO @keycol, @datacol; WHILE @@FETCH_STATUS = 0 BEGIN PRINT 'Handling keycol: ' + CAST(@keycol AS VARCHAR(10)) + ', datacol: ' + @datacol; FETCH NEXT FROM @C INTO @keycol, @datacol; END END GO
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Note You can use either the keyword FOR or the keyword AFTER to define an AFTER trigger .
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Inside Microsoft SQL Server 2008: T-SQL Programming
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This trigger simply prints the values provided in each new row inserted by the triggering INSERT action . It demonstrates how to deal with each row individually . The trigger then counts the number of rows returned by a TOP (2) query against inserted, and stores the result in a variable called @rc . Possible result values are 0, 1, and 2, indicating that zero, one, or more rows, respectively, were affected by the action that caused the trigger to fire . Note Prior to SQL Server 2008 I simply evaluted the @@rowcount function within the trigger
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in order to tell how many rows were affected by the statement that caused the trigger to fire . However, in SQL Server 2008, when you evaluate @@rowcount in an INSERT, UPDATE, or DELETE trigger that was fired due to a MERGE statement, you will get the total number of rows affected by MERGE . This number includes all actions not just the specific one that caused the trigger to fire . Since you cannot rule out running the MERGE statement in your system, you can t rely on @@rowcount within a trigger in SQL Server 2008 . Instead, you should query inserted or deleted as I demonstrated .
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If zero rows were affected, the trigger returns . If one row was affected, the code uses an assignment SELECT to grab the values from the row inserted into local variables . If multiple rows were affected, the code uses a cursor to iterate through the multiple rows in inserted . In each iteration, the code prints the values from the current row and fetches the values from the next row . To test the trigger, first run the following code, which inserts zero rows:
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INSERT INTO dbo.T1 SELECT 1, 'A' WHERE 1 = 0;
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As expected, you get no output from the trigger . Next, insert a single row:
INSERT INTO dbo.T1 SELECT 1, 'A';
You get the following output:
Handling keycol: 1, datacol: A
Finally, insert multiple rows:
INSERT INTO dbo.T1 VALUES (2, 'B'), (3, 'C'), (4, 'D');
You get the following output:
Handling keycol: 4, datacol: D Handling keycol: 3, datacol: C Handling keycol: 2, datacol: B
When you re done, run the following code for cleanup:
IF OBJECT_ID('dbo.T1', 'U') IS NOT NULL DROP TABLE dbo.T1;
4 Triggers
Identifying the Type of Trigger
In some cases you may prefer to create one trigger for multiple action types but you still want to be able to identify the type of action that fired the trigger . To identify the type of action that fired the trigger, you can inspect inserted and deleted . Of course, if zero rows were affected, both tables will be empty, but in such a case you d typically rather do nothing . If at least one row was affected, you can check which table contains rows to determine the type of change . As a result of an INSERT action, you will find rows only in inserted; for a DELETE action, you will find rows only in deleted; for an UPDATE action, you will find rows in both tables . Remember also that a MERGE statement may cause multiple trigger types to be fired . To demonstrate this, first create the table T1 by running the following code:
IF OBJECT_ID('dbo.T1', 'U') IS NOT NULL DROP TABLE dbo.T1; CREATE TABLE dbo.T1 ( keycol INT NOT NULL PRIMARY KEY, datacol VARCHAR(10) NOT NULL );
Run the following code to create the trigger trg_T1_iud:
CREATE TRIGGER trg_T1_iud ON dbo.T1 FOR INSERT, UPDATE, DELETE AS DECLARE @i AS INT = (SELECT COUNT(*) FROM (SELECT TOP (1) * FROM inserted) AS I); DECLARE @d AS INT = (SELECT COUNT(*) FROM (SELECT TOP (1) * FROM deleted) AS D); IF @i = PRINT ELSE IF PRINT ELSE IF PRINT ELSE PRINT GO 1 AND @d = 'UPDATE of @i = 1 AND 'INSERT of @i = 0 AND 'DELETE of 1 at @d at @d at
least one row identified'; = 0 least one row identified'; = 1 least one row identified';
'No rows affected';
The trigger s code declares the variables @i and stores within it the value 1 if at least one row appears in inserted and 0 otherwise . Similarly, the trigger declares the variables @d and stores within it the value 1 if at least one row appears in deleted and 0 otherwise . The trigger then inspects the values of @i and @d to determine which action caused it to fire . If both variables are equal to 1, an UPDATE action that affected at least one row caused the current instance of the trigger to fire . If @i is equal to 1 and @d is equal to 0, an INSERT action that affected at least one row caused the trigger to fire . If @i is equal to 0 and @d is equal to 1,
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