CHECK

CHECK cheklovi a ga joylashtirilishi mumkin bo‘lgan qiymatni cheklaydi ustun.

SQL CHECK on CREATE TABLE

Quyidagi SQL "Persons" jadvali yaratilayotganda "Age" ustunida CHECK cheklovini yaratadi. CHECK cheklovi 18 yoshdan kichik shaxs bo‘lishiga yo‘l qo‘ymaydi:

MySQL:

CREATE TABLE Persons (
Age int,
CHECK (Age>=18)
);

SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
Age int CHECK (Age>=18)
);

CHECK cheklovini nomlashga ruxsat berish va bir nechta ustunlarda CHECK cheklovini aniqlash uchun quyidagi SQL sintaksisidan foydalaning:

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    Age int,
    City varchar(255),
    CONSTRAINT CHK_Person CHECK (Age>=18 AND City='Sandnes')
);

SQL CHECK on ALTER TABLE

Jadval allaqachon yaratilgan bo‘lsa, "Age" ustunida CHECK cheklovini yaratish uchun quyidagi SQL’dan foydalaning:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CHECK (Age>=18);

CHECK cheklovini nomlashga ruxsat berish va bir nechta ustunlarda CHECK cheklovini aniqlash uchun quyidagi SQL sintaksisidan foydalaning:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CONSTRAINT CHK_PersonAge CHECK (Age>=18 AND City='Sandnes');

CHECK cheklovini o‘chirish (DROP)

CHECK cheklovini o‘chirish uchun quyidagi SQL’dan foydalaning:

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT CHK_PersonAge;

MySQL:

ALTER TABLE Persons
DROP CHECK CHK_PersonAge;

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