如何 select 来自两个不同表的不同值

Question

我有两个 table table1:

id   name   posId   Mid
1    sam    1       10
2    sid    1       10
3    jeet   1       10

table2:

id   name   posid   Mid
1    Anin   2       10
2    Nir    2       10
3    jeev   2       10

我想要一个table喜欢...

posid
1
2

即；我想通过加入 table1 和 table2 来获得不同的 "posid"，其中 "Mid" 对于 table1 和 table2

Answer 1

你可以这样做：

select distinct t1.posId
from t1
where not exists (select 1 from t2 where t2.posId = t1.posId)
union all
select distinct t2.posId
from t2
where not exists (select 1 from t1 where t2.posId = t1.posId);

我想我误解了这个问题。您可以使用 join:

select t1.posid, t2.posid
from t1 join
     t2
     on t1.mid = t2.mid;

要将其作为列，您需要逆透视。这是一种方法：

select distinct (case when n.which = 1 then t1.posid else t2.posid end) as posid
from t1 join
     t2
     on t1.mid = t2.mid cross join
     (select 1 as which union all select 2 as which) n

Answer 2

我知道您希望两个表的 posid 不同。

这效率不高但有效：

select distinct aa.posid
from
    (select distinct table1.posid as posid
       from table1
       join table2
         on table1.mid=table2.mid
     UNION ALL
     select distinct table2.posid as posid
       from table1
       join table2
         on table1.mid=table2.mid) aa

Answer 3

您可以将 join 与 union

一起使用

select t1.posid
from t1 join t2 on t1.mid = t2.mid
union
select t2.posid
from t1 join t2 on t1.mid = t2.mid

如何 select 来自两个不同表的不同值

how to select distinct values from two different tables

sql

distinct-values