IN条件左侧的多列

问题描述 投票:1回答:2

这是一个有效的声明:

SELECT foo FROM table1 WHERE
  column1 IN (SELECT bar FROM table2) AND
  column2 IN (SELECT bar FROM table2)

但有没有什么办法可以避免重复SELECT bar FROM table2声明,使其更简单,更经济?

我的意思是这样的:

SELECT foo FROM table1 WHERE
  «column1 and also column2» IN (SELECT bar FROM table2)
sql postgresql sql-in
2个回答
4
投票

您可以将相关子查询与EXISTS运算符一起使用

select *
from table1 t1
where exists (select *
              from table2 t2
              where t2.bar in (t1.column1, t1.column2));

如果两列都与table2.bar中的值匹配,则可以使用以下列:

select *
from table1 t1
where exists (select *
              from table2 t2
              where t2.bar = t1.column1
                and t2.bar = t1.column2);

3
投票

您可以使用聚合:

select *
from table1
where exists (
    select 1
    from table2
    where table2.bar in (table1.column1, table1.column2)
    having count(distinct bar) = case when table1.column1 = table1.column2 then 1 else 2 end
);

因此,如果table1包含(foo, bar)对,而table2包含值(foo), (baz)则不匹配。

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