UNIQUE

UNIQUE cheklovi hammasini ta’minlaydi ustundagi qiymatlar noyobdir.

CREATE TABLE da SQL UNIQUE cheklovi

Quyidagi SQL "Persons" jadvali yaratilayotganda "ID" ustunida UNIQUE cheklovini yaratadi:

SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL UNIQUE,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int
);

MySQL:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    UNIQUE (ID)
);

UNIQUE chekloviga nom berish va UNIQUE cheklovini bir nechta ustunda aniqlash uchun quyidagi SQL sintaksisidan foydalaning:

MySQL / SQL Server / Oracle / MS Access:

CREATE TABLE Persons (
    ID int NOT NULL,
    LastName varchar(255) NOT NULL,
    FirstName varchar(255),
    Age int,
    CONSTRAINT UC_Person UNIQUE (ID,LastName)
);

ALTER TABLE da SQL UNIQUE cheklovi

Jadval allaqachon yaratilganda "ID" ustunida UNIQUE cheklovini yaratish uchun quyidagi SQL dan foydalaning:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD UNIQUE (ID);

UNIQUE chekloviga nom berish va UNIQUE cheklovini bir nechta ustunda aniqlash uchun quyidagi SQL sintaksisidan foydalaning:

MySQL / SQL Server / Oracle / MS Access:

ALTER TABLE Persons
ADD CONSTRAINT UC_Person UNIQUE (ID,LastName);

UNIQUE cheklovini o‘chirish (DROP)

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

MySQL:

ALTER TABLE Persons
DROP INDEX UC_Person;

SQL Server / Oracle / MS Access:

ALTER TABLE Persons
DROP CONSTRAINT UC_Person;

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