Tuesday, August 19, 2008

INSTEAD OF INSERT Triggers

CREATE TABLE BaseTable
(PrimaryKey int PRIMARY KEY IDENTITY(1,1),
Color nvarchar(10) NOT NULL,
Material nvarchar(10) NOT NULL,
ComputedCol AS (Color + Material)
)
GO
--Create a view that contains all columns from the base table.
CREATE VIEW InsteadView
AS SELECT PrimaryKey, Color, Material, ComputedCol
FROM BaseTable
GO
--Create an INSTEAD OF INSERT trigger on the view.
CREATE TRIGGER InsteadTrigger on InsteadView
INSTEAD OF INSERT
AS
BEGIN
--Build an INSERT statement ignoring inserted.PrimaryKey and
--inserted.ComputedCol.
INSERT INTO BaseTable
SELECT Color, Material
FROM inserted
END
GO

DDL TRIGGER

CREATE TRIGGER safety
ON DATABASE
FOR DROP_TABLE, ALTER_TABLE
AS
PRINT 'You must disable Trigger "safety" to drop or alter tables!'
ROLLBACK ;
---------------------------
create table mytable
(
id int,
nam char(10)
)
---------------------------
drop table mytable
---------------------------
drop trigger safety on database
-----------------------------
drop table mytable

Monday, August 18, 2008

DBCC SHRINKFILE (Transact-SQL)

A. Shrinking a data file to a specified target size

The following example shrinks the size of a data file named DataFile1 in the UserDB user database to 7 MB.

USE UserDB;
GO
DBCC SHRINKFILE (DataFile1, 7);
GO

B. Shrinking a log file to a specified target size

The following example shrinks the log file in the AdventureWorks database to 1 MB. To allow the DBCC SHRINKFILE command to shrink the file, the file is first truncated by setting the database recovery model to SIMPLE.

USE AdventureWorks;
GO
-- Truncate the log by changing the database recovery model to SIMPLE.
ALTER DATABASE AdventureWorks
SET RECOVERY SIMPLE;
GO
-- Shrink the truncated log file to 1 MB.
DBCC SHRINKFILE (AdventureWorks_Log, 1);
GO
-- Reset the database recovery model.
ALTER DATABASE AdventureWorks
SET RECOVERY FULL;
GO

C. Truncating a data file

The following example truncates the primary data file in the AdventureWorks database. The sys.database_files catalog view is queried to obtain the file_id of the data file.

USE AdventureWorks;
GO
SELECT file_id, name
FROM sys.database_files;
GO
DBCC SHRINKFILE (1, TRUNCATEONLY);

D. Emptying a file

The following example demonstrates the procedure for emptying a file so that it can be removed from the database. For the purposes of this example, a data file is first created and it is assumed that the file contains data.

USE AdventureWorks;
GO
-- Create a data file and assume it contains data.
ALTER DATABASE AdventureWorks
ADD FILE (
NAME = Test1data,
FILENAME = 'C:\t1data.ndf',
SIZE = 5MB
);
GO
-- Empty the data file.
DBCC SHRINKFILE ('Test1data', EMPTYFILE);
GO
-- Remove the data file from the database.
ALTER DATABASE AdventureWorks
REMOVE FILE Test1data;
GO

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