unique constraint mssql
USE AdventureWorks2012;
GO
CREATE TABLE Production.TransactionHistoryArchive4
(
TransactionID int NOT NULL,
CONSTRAINT AK_TransactionID UNIQUE(TransactionID)
);
GOunique constraint mssql
USE AdventureWorks2012;
GO
CREATE TABLE Production.TransactionHistoryArchive4
(
TransactionID int NOT NULL,
CONSTRAINT AK_TransactionID UNIQUE(TransactionID)
);
GOalter unique key sql query
ALTER TABLE Product ADD CONSTRAINT AK_Product_ProductCode UNIQUE( ProductCode )
ALTER TABLE Product ADD CONSTRAINT AK_Product_ProductStamp UNIQUE( ProductStamp )primary key and unique key in sql
What is the difference between UNIQUE and PRIMARY KEY constraints?
There should be only one PRIMARY KEY
in a table whereas there can be
any number of UNIQUE Keys.
PRIMARY KEY doesn’t allow NULL
values whereas Unique key allows NULL values.unique key in sql
Unique Key:
Only unique value and also can contain NULLCopyright © 2021 Codeinu
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