Primary Key

Question

What is primary key in sql and what is it for?

Answer 1

Europa learn from w3 school.
https://www.w3schools.com/sql/sql_primarykey.asp

Answer 2

Primary key : It's an Entity that is necessary to uniquely identify the each tuple in the table.
»primary key generally should not be null.
»Primary key may be null for a tuple if and only if it is the only tuple that exists in the table with primary key with null .

Answer 3

Primary key is the combination of unique and notnull i.e., primary key should be unique and not null represents the column should contain some value.

Answer 4

Primary key are used to set a unique value for a columm on a table, that can be used with other table using SELECT statement. Try look for relational databases, that's all about.

Answer 5

A primary key is a field in a table which uniquely identifies each row/record in a database table.

Answer 6

In simple terms, a primary key is a column which uniquely identifies each record in the table. It can not be null and cannot have duplicate values.

Answer 7

primary key is combination of not null and unique. not null represents that the column should exist some value and unique key represent, the column should not have repeated value.

Answer 8

Primary key uniquely identify column and doesn’t allow null value