连接查询

1、差集。

select c.id,c.num from 
 (select a.`村寨id` id, count(1) num from 农户签约详细信息 a group by a.`村寨id`) c 
left join
 (select b.`村寨id` id, count(1) num from 房间 b group by b.`村寨id`)d 
on c.id = d.id
 where c.num  < d.num;

SELECT DISTINCT t.id FROM

(
 select a.`村寨id` id, count(1) num from 农户签约详细信息 a group by a.`村寨id` 
UNION ALL
 select b.`村寨id` id, count(1) num from 房间 b group by b.`村寨id`
) t
GROUP BY t.id,t.num 
HAVING count(*) <2;