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what is primary key?

Question asked by rajmanisha in #Coffee Room on Jul 10, 2017
rajmanisha · Jul 10, 2017
what is primary key? Posted in: #Coffee Room
Kaustubh Katdare
Kaustubh Katdare · Jul 10, 2017
Rank A1 - PRO
what is primary key?
How about adding a little more reference to your question? Are we talking about databases here?
Neeraj Sharma
Neeraj Sharma · Jul 10, 2017
Rank B2 - LEADER
what is primary key?
Shweta Chauhan
Shweta Chauhan · Jul 11, 2017
Rank D2 - MASTER
In context of DBMS, primary key is a column in a table that uniquely identifies the rows of that table.Several rows of a table can have similar value for a column but in case if that column is a primary key for that table, it can't be same.
In addition to uniquely identifying a row, it also ensures that there cannot be any null value in that column(if it is the primary key for that table)
A simple example:
Here Roll No. column is the primary key of this table so values in that column cannot be same,but name and marks can have similar values.
vinod12345madhu · Aug 15, 2017
Rank C2 - EXPERT
what is primary key?
your aadhar number (Social security number ) in the US, Driving license number etc all can be your your primary key.

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