How do you define a primary key?

How do you establish a primary key?

Create a primary key1In Object Explorer, right-click the table to which you want to add a unique constraint, and click Design.2In Table Designer, click the row selector for the database column you want to define as the primary key. ... 3Right-click the row selector for the column and select Set Primary Key.Create Primary Keys in SQL Server - Microsoft Docs

What is a primary key with example?

A primary key is a column -- or a group of columns -- in a table that uniquely identifies the rows in that table. For example, in the table below, CustomerNo, which displays the ID number assigned to different customers, is the primary key.

How do you identify a primary key?

Columns that have a high percentage of uniqueness, as well as at least one foreign key candidate, make the best primary key candidates. Identify the columns that have the highest uniqueness percentage and assign one of the columns as the primary key. You might only have one primary key per table.

Why we define primary key?

The main purpose of primary key is to identify the uniqueness of a row, where as unique key is to prevent the duplicates, following are the main difference between primary key and unique key. Primary Key : There can only be one primary key for a table. The primary key consists of one or more columns.