Comments on: Drop all foreign keys

By: Kristof Elst

Kristof Elst — Mon, 16 Jan 2012 08:51:38 +0000

Thanks for your article.

Here’s another way to do it, without resorting to a blighted cursor.

http://www.sentientbeings.com/2012/01/drop-all-foreign-keys-on-a-database-and-optionally-drop-all-tables/

By: rajendra.more999@hotmail.com

rajendra.more999@hotmail.com — Sat, 12 Nov 2011 11:07:34 +0000

Thanks Really working …

By: tom

tom — Sat, 17 Sep 2011 00:57:00 +0000

Going to have try this script next time this problem comes up, thanks!

By: Noor

Noor — Fri, 15 Jul 2011 13:34:01 +0000

Its better to disable foreign keys. If you want to disable all constraints in the database just run this code:
– disable all constraints
EXEC sp_msforeachtable “ALTER TABLE ? NOCHECK CONSTRAINT all”

– enable all constraints
exec sp_msforeachtable @command1=”print ‘?’”, @command2=”ALTER TABLE ? WITH CHECK CHECK CONSTRAINT all”

By: Arno

Arno — Wed, 13 Jul 2011 05:33:29 +0000

Added some brackets for the “weird” table names:

–ENJOY
DECLARE @sqlForeignKeys VARCHAR(MAX)

SELECT @sqlForeignKeys = ISNULL(@sqlForeignKeys,”) +
‘ALTER TABLE dbo.[' + OBJECT_NAME(FK.parent_object_id) + '] DROP CONSTRAINT [' + FK.name + '];’ + CHAR(10)
FROM SYS.FOREIGN_KEYS FK

PRINT(@sqlForeignKeys)
–EXEC(@sqlForeignKeys)

By: Timmy

Timmy — Tue, 17 May 2011 07:42:12 +0000

– ENJOY
DECLARE @sqlForeignKeys VARCHAR(MAX)

SELECT @sqlForeignKeys = ISNULL(@sqlForeignKeys,”) +
‘ALTER TABLE dbo.’ + OBJECT_NAME(FK.parent_object_id) + ‘ DROP CONSTRAINT ‘ + FK.name + ‘;’ + CHAR(10)
FROM SYS.FOREIGN_KEYS FK

PRINT(@sqlForeignKeys)
–EXEC(@sqlForeignKeys)

By: chris

chris — Wed, 04 May 2011 02:36:23 +0000

Combining ideas [1] and [7]

DECLARE @fkdel varchar(512)
DECLARE FkCrsr CURSOR FOR
SELECT ‘ALTER TABLE [' + TABLE_SCHEMA + '].[' + TABLE_NAME +
'] DROP CONSTRAINT [' + CONSTRAINT_NAME +']‘
FROM information_schema.table_constraints
WHERE CONSTRAINT_TYPE = ‘FOREIGN KEY’

open FkCrsr
fetch next from FkCrsr into @fkdel
while @@FETCH_STATUS = 0
begin
print @fkdel
exec (@fkdel)
fetch next from FkCrsr into @fkdel
end

close FkCrsr
deallocate FkCrsr
go

By: Andy

Andy — Tue, 04 Jan 2011 21:54:28 +0000

Sorry the last post was missing the in the where and had the wrong quotes.

–DROP CONSTRAINTS
DECLARE FK_cursor CURSOR
FOR
SELECT S.name, F.name, T.name
FROM sys.foreign_keys F
JOIN sys.tables T ON F.parent_object_id=T.object_id
JOIN sys.schemas S ON S.schema_id=T.schema_id
WHERE
T.name in (‘table1′,’table2′,’table3′)
OPEN FK_cursor
DECLARE @shemaName sysname, @fkName sysname, @tableName sysname
FETCH NEXT FROM FK_cursor INTO @shemaName, @fkName, @tableName
WHILE (@@FETCH_STATUS -1)
BEGIN
PRINT ‘Dropping constraint ‘ + @fkName + ‘ on table ‘ + @shemaName + ‘.’ + @tableName
EXECUTE (‘ALTER TABLE [' + @shemaName + '].[' + @tableName + '] DROP CONSTRAINT [' + @fkName + ']‘)
FETCH NEXT FROM FK_cursor INTO @shemaName, @fkName, @tableName
END

By: Andy

Andy — Tue, 04 Jan 2011 21:47:01 +0000

Why not take it a step further and execute the alter automatically. Especially if it is part of a maintenance job that performs a truncate on the tables.

DECLARE FK_cursor CURSOR
FOR
SELECT S.name, F.name, T.name
FROM sys.foreign_keys F
JOIN sys.tables T ON F.parent_object_id=T.object_id
JOIN sys.schemas S ON S.schema_id=T.schema_id
WHERE
T.name in (‘PayldSeg’,'PayldDest’,'Payld’,'DataPkgUsrStsHist’,'DataPkgUsr’,'DataPkg’,'DataPkgRqstQueUsr’,'ServPrcsMsg’,'DataPkgRqstQue’)
OPEN FK_cursor
DECLARE @shemaName sysname, @fkName sysname, @tableName sysname
FETCH NEXT FROM FK_cursor INTO @shemaName, @fkName, @tableName
WHILE (@@FETCH_STATUS -1)
BEGIN
PRINT ‘Dropping constraint ‘ + @fkName + ‘ on table ‘ + @shemaName + ‘.’ + @tableName
EXECUTE (‘ALTER TABLE [' + @shemaName + '].[' + @tableName + '] DROP CONSTRAINT [' + @fkName + ']‘)
FETCH NEXT FROM FK_cursor INTO @shemaName, @fkName, @tableName
END

By: tom

tom — Wed, 24 Nov 2010 19:12:36 +0000

Good point, wrapping the names in brackets would avoid issues. I always avoid naming my tables such that it would be a problem, makes life ever so much easier but one cannot count on others to do the same.