最好写个触发器:
create trigger test on 大类表
for delete
as
delete 小类表 where 所属大类id in (select 大类id from deleted)
create trigger test on 大类表
for delete
as
delete 小类表 where 所属大类id in (select 大类id from deleted)
create trigger test on 大类表
for delete
as
delete 小类表 where 所属大类id in (select 大类id from deleted)