SQL SERVERDE CHECK CONSTRAINT ISTIFADESI

CHECHK constraint vasitesile istenilen sutunda istediyimiz formata uygun melumatin daxil edilmesini mueyyen ede bilerik.

CREATE TABLE Student
(
P_Id int NOT NULL CHECK (P_Id>0),
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255)
)

Burada CHECK constraint P_Id sutununda yalniz 0-dan boyuk integer reqemler daxil olunmasini mueyyen edir.Eger 0 daxil etsek o zaman error ile qarsilacagiq.CHECK hemcinin muxtelif sutunlar uzerinede qoyula biler.Meselen:

CREATE TABLE Student
(
P_Id int NOT NULL,
LastName varchar(255) NOT NULL,
FirstName varchar(255),
Address varchar(255),
City varchar(255),
CONSTRAINT chk_Person CHECK (P_Id>0 AND City='Sandnes')
)

Cedvel yarandiqdan sonra check constrainti daxil etmek istesek:

ALTER TABLE Student
ADD CHECK (P_Id>0)

Muxtelif sutunlara qoymaq istesek:

ALTER TABLE Student
ADD CONSTRAINT chk_Person CHECK (P_Id>0 AND City='Sandnes')

Constrainti silmek istesek:

ALTER TABLE Student
DROP CONSTRAINT chk_Person