How to Find a SQL Server Table's Primary Key?

Finding the Primary Key of a SQL Server Table

Knowing a table's primary key is essential for database management and data integrity. SQL Server offers several methods to identify this key.

Using Information Schema Views

A simple and effective method uses the INFORMATION_SCHEMA views. This query combines data from TABLE_CONSTRAINTS and CONSTRAINT_COLUMN_USAGE to pinpoint the primary key columns:

<code class="language-sql">SELECT Col.Column_Name
FROM INFORMATION_SCHEMA.TABLE_CONSTRAINTS Tab
INNER JOIN INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE Col ON Col.Constraint_Name = Tab.Constraint_Name
WHERE Col.Table_Name = Tab.Table_Name
AND Tab.Constraint_Type = 'PRIMARY KEY'
AND Col.Table_Name = '<your table name>'</code>

Here's a breakdown:

• INFORMATION_SCHEMA.TABLE_CONSTRAINTS: Provides details on table constraints.
• INFORMATION_SCHEMA.CONSTRAINT_COLUMN_USAGE: Shows which columns are involved in each constraint.
• Tab.Constraint_Type = 'PRIMARY KEY': Filters results to only include primary key constraints.
• <your table name>: Replace this with the actual name of your target table.

This query efficiently retrieves the primary key column(s) for the specified table.

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