怎么做sql减法

Question

有没有办法用类似的语法执行以下操作？

select count(*) FROM main_iteminstance where item_type_id='TITLE'
-
select count(*) FROM main_catalog

换句话说，count1 减去 count2。

Answer 1

没试过，但你可以通过使用子查询来实现，如下所示：

select (query1.cnt-query2.cnt) from (select count(*) as cnt from ...) as query1, (select count(*) as cnt from ...) as query2