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Решение:

EXEC sp_msforeachtable "ALTER TABLE ? NOCHECK CONSTRAINT all"
Подробнее:
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"
To switch them back on, run: (the print is optional of course and it is just listing the tables)
-- enable all constraints
exec sp_msforeachtable @command1="print '?'", @command2="ALTER TABLE ? WITH CHECK CHECK CONSTRAINT all"
http://stackoverflow.com/questions/159038/can-foreign-key-constraints-be-temporarily-disabled-using-t-sql