Primary key

Question

Can a primary key contains more than one column?

Arjun Panwar · Answer

Yes a primary key can contain more than one column. Example: CREATE TABLE Persons ( P_Id int NOT NULL, LastName varchar(255) NOT NULL, FirstName varchar(255), Address varchar(255), City varchar(255), CONSTRAINT pk_PersonID PRIMARY KEY (P_Id,LastName) ) Note: In the example above there is only ONE PRIMARY KEY (pk_PersonID). However, the value of the pk_PersonID is made up of two columns (P_Id and LastName).

Priya Linge · Answer

Hi, 1.NO, A table can have Only One primary key. 2.But a table can have any number of composite primary key's 3. A primary key can have more than one column.it is called Composite Primary Key. 4. The primary key is one of the unique keys defined on a table, but is selected to be the key of first importance. There can be only one primary key on a table. 5. Composite key : a primary key containing more than one column . 6.we can create composite primary key upto 16 columns only. Please check below link for more information. http://publib.boulder.ibm.com/infocenter/db2luw/v8/index.jsp?topic=/com.ibm.db2.udb.doc/admin/c0004799.htm Hope this will help you. Thanks.

Akash Ahlawat · Answer

Thanks Arjun..

Pravin More · Answer

Hi Akash, You can only have one primary key, but you can have multiple columns in your primary key. CREATE TABLE userdata ( userid integer, userdataid integer, info char(200) primary key (userid, userdataid) ); Thanks, Pravin

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