一种检查SQL 2005中是否存在外键的方法

Question

Is there an easy way to check if a foreign key exists for a column in a table? I am writing a script which will add the foreign key only if it does not exist.

Answer 1

You can use this script:

IF EXISTS (SELECT * 
           FROM sys.foreign_keys 
           WHERE object_id = OBJECT_ID(N'[dbo].[FK_NAME]') 
             AND parent_object_id = OBJECT_ID(N'[dbo].[MyTable]'))
BEGIN
    -- do stuff
END

This can be done if you expand out the table and right click on an existing FK and choose script key as "DROP TO" and then you will get a generated script from SQL.

Answer 2

Woo-hoo! I just spent the past two days doing this.

IF NOT EXISTS ( SELECT  name
                FROM    sys.foreign_keys
                WHERE   name = 'FK_Name' ) 
    ALTER TABLE table_name ADD CONSTRAINT FK_Name FOREIGN KEY (idcol) 
                           REFERENCES OtherTable(idcol)