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_IdLastName) ) 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