Question

我有一个包含许多表的数据库..每个表都只存储了ID。现在我想做的是：

SELECT id FROM table1, table2, table3
GROUP BY id;

但我也希望通过降低发生顺序对它们进行排序。

例如，所有3个表中的ID应显示在顶部，而仅出现在一个表中的ID应位于底部。关于如何做到这一点的任何线索？

Answer 1

试试这个

select id from
(
    SELECT id FROM table1
    union all
    select id from table2
    union all
    select id from table3 
) as t
GROUP BY id
order by count(id) desc

Answer 2

select sum(t1.id IS NOT NULL,t2.id IS NOT NULL, t3.id IS NOT NULL) as total,t1.id from table1 as t1 join table2 as t2 on t1.id=t2.id join table3 as t3 on t3.id = t1.id order by total desc;

我不确定你的问题，但这可以帮助

Answer 3

select id from
(
    SELECT id FROM table1
    union all
    select id from table2
    union all
    select id from table3 
) as t
GROUP BY id
order by id desc

按表中出现次数排序

3 个答案: