IN 条件左侧的多列

Question

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)

但是有什么办法可以避免重复SELECT bar FROM table2语句，使它更简单、更经济吗？

我的意思是这样的：

SELECT foo FROM table1 WHERE
  «column1 and also column2» IN (SELECT bar FROM table2)

Answer 1

您可以使用带有 EXISTS 运算符的相关子查询

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

如果两列都应与 table2.bar 中的值匹配，则可以使用以下内容：

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

Answer 2

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
);

所以如果表 1 包含对 (foo, bar) 并且表 2 包含值 (foo), (baz) 它 将不会 匹配.

IN 条件左侧的多列

Multiple columns on left side of IN condition

sql

postgresql

sql-in