sql 使用union，intersection或difference运算符组合查询（来自http://www.postgresql.org/docs/9.4/static/queries-union

Posted 2021-05-13

(select ... from ...) foo union (select ... from ...) bar;
(select ... from ...) foo intersect (select ... from ...) bar;
(select ... from ...) foo except (select ... from ...) bar;