Composite Key in SQL Server

ByHariharan Rajendran

Composite Key in SQL Server

This article is about to create primary key on multiple columns. Go through my previous article here to know about primary key and how to create it.

There are many scenarios where we need to create primary key on multiple columns.

For example, if you take E-learning sites. They are offering free trail and asking us to sign up using our email id and phone number to experience the free trail.

Once trail period is completed then we cannot apply for one more trail using same email id and phone number because the system will not allow inserting same combination again.

Primary key on multiple columns is called “Composite Key”.

Composite Key Syntax:

CREATE TABLE SAMPLE_TABLE
(COL1 int,
COL2 varchar(30),
COL3 varchar(50),
PRIMARY KEY (COL1, COL2));

Example.

CREATE TABLE USERS

(UserId int,

Name varchar(50),

EmailId varchar(50),

Phonenumber varchar(50)

PRIMARY KEY (EmailId, Phonenumber))

 

composite key

About the Author

Hariharan Rajendran author

Hariharan Rajendran is a MVP in Data Platform and Microsoft Certified Trainer with 10+ years of experience in Database, BI and Azure platforms. Hariharan is also an active community leader, speaker & organizer and leads the Microsoft PUG (Power BI User Group – Chennai), SQLPASS Power BI Local Group – Chennai and an active speaker in SQL Server Chennai User Group and also a leader in Data Awareness Program worldwide events. Hariharan also frequently blogs (www.dataap.org/blog), provides virtual training (on ad-hoc basis) on Microsoft Azure, Database Administration, Power BI and database development to worldwide clients/audience.

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