-- disable referential integrity
EXEC sp_MSForEachTable 'ALTER TABLE ? NOCHECK CONSTRAINT ALL'
GO

EXEC sp_MSForEachTable '
IF OBJECTPROPERTY(object_id(''?''), ''TableHasForeignRef'') = 1
DELETE FROM ?
else
TRUNCATE TABLE ?
'
GO

-- enable referential integrity again
EXEC sp_MSForEachTable 'ALTER TABLE ? CHECK CONSTRAINT ALL'
GO