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Asked: 2026-05-11T15:18:00+00:00

My end goal is to accomplish something like: CREATE FOREIGN KEY IF NOT EXISTS

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My end goal is to accomplish something like:

CREATE FOREIGN KEY IF NOT EXISTS FOREIGN KEY

Since that statement doesn’t appear to exist, I’m attempting to sort of kludge it together.

I have a statement that will return the FK name if it exists:

SELECT f.name AS ForeignKey FROM sys.foreign_keys AS f  WHERE OBJECT_NAME(f.parent_object_id) = 'myTableName'

And I have a statement that adds the desired foreign key:

ALTER TABLE myTableName WITH CHECK  ADD CONSTRAINT [FK_myTableName_otherTable]  FOREIGN KEY([columnName])  REFERENCES otherTable ([otherColumn])

I just can’t, for the life of me, figure out how to mash them together into a single statement.

It’s an absolute requirement that the solution work in both MS SQL 2000 as well as MS SQL 2005.

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1 Answer

  1. sys.foreign_keys was introduced in SQL Server 2005. You’ll have to use sysobjects to be compatible with both SQL Server 2000 & 2005.

    Try this SQL:

    IF NOT EXISTS (     SELECT NULL FROM sysobjects      WHERE name = 'FK_myTableName_otherTable'      AND parent_obj = OBJECT_ID(N'myTableName')) ALTER TABLE myTableName WITH CHECK  ADD CONSTRAINT [FK_myTableName_otherTable]  FOREIGN KEY([columnName])  REFERENCES otherTable ([otherColumn])
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