访问postgresql中的列别名

Question

理解查询别名在postgresql中的工作方式有点麻烦.我有以下内容:

SELECT DISTINCT robber.robberid,
                nickname,
                Count(accomplices.robberid) AS count1
FROM   robber
       INNER JOIN accomplices
               ON accomplices.robberid = robber.robberid
GROUP  BY robber.robberid,
          robber.nickname
ORDER  BY Count(accomplices.robberid) DESC;


 robberid |            nickname            | count1 
----------+--------------------------------+--------
       14 | Boo Boo Hoff                   |      7
       15 | King Solomon                   |      7
       16 | Bugsy Siegel                   |      7
       23 | Sonny Genovese                 |      6
        1 | Al Capone                      |      5
 ...

我可以使用as命令重命名"count1"列,但我似乎无法在查询中再次引用它？我试图在此查询结束时包含一个HAVING命令,以仅查询计数小于最大值一半的对象.

这是家庭作业,但我不是要求答案只是指向我如何在另一个子句中包含count1列的指针.

有人可以帮忙吗？

Answer 1

通常,您不能在查询中稍后引用聚合列的别名,并且必须重复聚合

如果您确实想使用其名称,可以将查询包装为子查询

SELECT * 
FROM
(
    SELECT DISTINCT robber.robberid, nickname, count(accomplices.robberid)  
    AS count1 FROM robber                   
    INNER JOIN accomplices  
    ON accomplices.robberid = robber.robberid  
    GROUP BY robber.robberid, robber.nickname  
) v
ORDER BY count1 desc