How to Temporarily Disable and Re-enable Database Constraints in MS SQL?

Temporarily Managing Database Constraints in MS SQL Server

Disabling constraints temporarily in Microsoft SQL Server can streamline database operations, especially when transferring data. This guide details methods for temporarily disabling and re-enabling constraints.

Disabling Constraints

Individual Table Constraint Disabling (ALTER TABLE):

Use this command to disable constraints on a single table:

ALTER TABLE tableName NOCHECK CONSTRAINT ALL;

Database-Wide Constraint Disabling (sp_msforeachtable):

This stored procedure disables constraints across all tables within the database:

EXEC sp_msforeachtable 'ALTER TABLE ? NOCHECK CONSTRAINT ALL';

Re-enabling Constraints

Individual Table Constraint Re-enabling (ALTER TABLE):

Re-enable constraints on a specific table with this command:

ALTER TABLE tableName WITH CHECK CHECK CONSTRAINT ALL;

Database-Wide Constraint Re-enabling (sp_msforeachtable):

Re-enable constraints for all tables in the database using this stored procedure:

EXEC sp_msforeachtable 'ALTER TABLE ? WITH CHECK CHECK CONSTRAINT ALL';

Practical Application

The following example showcases the process of temporarily disabling and re-enabling constraints during a data copy operation:

-- Disable constraints on TableA and TableB
ALTER TABLE TableA NOCHECK CONSTRAINT ALL;
ALTER TABLE TableB NOCHECK CONSTRAINT ALL;

-- Copy data from TableA to TableB
INSERT INTO TableB SELECT * FROM TableA;

-- Re-enable constraints on TableA and TableB
ALTER TABLE TableA WITH CHECK CHECK CONSTRAINT ALL;
ALTER TABLE TableB WITH CHECK CHECK CONSTRAINT ALL;

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