How do I drop all foreign-key constraints on a table in Sql Server 2000?

Question

How do I drop all foreign-key constraints on a table in SQL Server 2000 using T-SQL?

Answer 1

I think you'll find that there is no easy way to drop constraints on a table in SQL Server 2000. That said, there are plenty of people who have written scripts that can identify and remove/disable/recreate foreign key constraints. One example is at http://www.mssqltips.com/tip.asp?tip=1376 - but I haven't tested it on SQL Server 2000.

EDIT: Here is another example that generates drop/create scripts for you.

Answer 2

If simply disabling constraints is an option here, you can use:

ALTER TABLE myTable NOCHECK CONSTRAINT all

then you can switch them back on simply using:

ALTER TABLE myTable WITH CHECK CHECK CONSTRAINT all

If you want to disable constrains in all tables you can use:

-- disable all constraints
EXEC sp_msforeachtable "ALTER TABLE ? NOCHECK CONSTRAINT all"

-- enable all constraints
exec sp_msforeachtable "ALTER TABLE ? WITH CHECK CHECK CONSTRAINT all"

More in the question: Can foreign key constraints be temporarily disabled using TSQL?

But if you need to drop constraints permanently you can use this script posted on databasejurnal.com.

Just modify it slightly to only drop the foreign keys

create proc sp_drop_fk_constraints
    @tablename sysname
as
-- credit to: douglas bass

set nocount on

declare @constname  sysname,
    @cmd  varchar(1024)

declare curs_constraints cursor for
    select  name
    from  sysobjects 
    where  xtype in ('F')
    and (status & 64) = 0
    and     parent_obj = object_id(@tablename)

open curs_constraints

fetch next from curs_constraints into @constname
while (@@fetch_status = 0)
begin
    select @cmd = 'ALTER TABLE ' + @tablename + ' DROP CONSTRAINT ' + @constname
    exec(@cmd)
    fetch next from curs_constraints into @constname
end

close curs_constraints
deallocate curs_constraints

return 0

Answer 3

Here you go: (not tested on SQL2000, but should be ok)

Generates 'disables':

SELECT  'IF EXISTS (SELECT * FROM sys.foreign_keys 
   WHERE object_id = OBJECT_ID(N''[dbo].' + FK +''') 
   AND parent_object_id = OBJECT_ID(N''[dbo].' + PT + ''')) 
   ALTER TABLE ' + PT + ' NOCHECK CONSTRAINT ' + FK + ';'
FROM 
(SELECT 
    OBJECT_NAME(constraint_object_id) as FK,
    OBJECT_NAME(parent_object_id) as PT
    FROM [sys].[foreign_key_columns] ) T
ORDER BY FK

Generates 'enables':

SELECT  'ALTER TABLE ' + PT + ' WITH CHECK CHECK CONSTRAINT ' + FK + ';'
FROM 
(SELECT 
    OBJECT_NAME(constraint_object_id) as FK,
    OBJECT_NAME(parent_object_id) as PT
    FROM [sys].[foreign_key_columns] ) T
ORDER BY FK

Update: Oops, I thought you wanted it for all tables :) You can just modify above for your single table.