访问子查询 SQL 中的字段

Question

我有一个相当复杂的查询，我正在处理多个嵌套的查询层。查询的要求之一是我在主查询中从子查询的子查询中访问一个字段。但是，由于中间查询中的聚合，我无法在该查询中包含该字段。

例如。

select a, d.x, f.v?
from b
  join (select a, max(z), min(z), Count(y) as x
        from c
          join (select a, Count(t) as v
                from e
               ) f 
            on f.a = c.a
            Group By a
            Having min(z) <> max(z)
       ) d 
     on d.a = b.a

这可能吗？

Answer 1

没有。

试试这个。基本上，在您上层时获取您需要的属性（如果需要，可以重命名它们），然后使用它们。

Select a, d.fa From b
join (select a,f.a fa from c
join (select a from e) f on f.a = c.a
) d on d.a = b.a

我还没有测试表。如果您发现更多问题，请在此处发布。

* 根据更新的问题进行编辑*

即使在这里，逻辑仍然相同，您必须使用...

select a, d.x, d.v?
from b
  join (select a, f.v, max(z), min(z), Count(y) as x
        from c
          join (select a, v
                from e
               ) f 
            on f.a = c.a
            Group By a, f.v
            Having min(z) <> max(z)
       ) d 
     on d.a = b.a

或者，如果您的数据库支持标量子查询，您可以使用..获取最终外部查询的值。

select a, d.x, (select v from e where e.a = b.a) f_v
from b
  join (select a, max(z), min(z), Count(y) as x
        from c
          join (select a, v
                from e
               ) f 
            on f.a = c.a
            Group By a
            Having min(z) <> max(z)
       ) d 
     on d.a = b.a

Answer 2

如果您只是将您关心的表（在本例中为 e）带回 From 子句，这可能更直接

SELECT a, 
       d.x, 
       e.v 
FROM   b 
       JOIN (SELECT a, 
                          MAX(z), 
                          MIN(z), 
                          COUNT(y) AS x 
                   FROM   c 
                          JOIN (SELECT a 
                                FROM   e) f 
                            ON f.a = c.a 
                   GROUP  BY a 
                   HAVING MIN(z) <> MAX(z)) d 
         ON d.a = b.a 
       JOIN (SELECT a, Count(t) as v
            FROM e
            GROUP BY A ) e
         ON e.a = d.a