Question

考虑PostgreSQL中的以下查询：

SELECT 
    a, b, 
   (A VERY LONG AND COMPLICATED SUBQUERY) AS c,
   (ANOTHER VERY LONG AND COMPLICATED SUBQUERY) AS d
FROM table

我想在c子句中设置d和WHERE，例如：

WHERE c AND d;

但据我所知，我只能这样做：

WHERE A VERY LONG AND COMPLICATED SUBQUERY) AND 
   (ANOTHER VERY LONG AND COMPLICATED SUBQUERY)

哪个是笨拙的，代码复制的，breaking the single-choice principle而且非常难看。

顺便说一下，同样的问题也适用于SELECT子句：我不能将缩写用于先前定义的子查询。

Answer 1

您可以使用子查询：

SELECT a,b,c,d FROM
    (SELECT 
        a, b, 
        (A VERY LONG AND COMPLICATED SUBQUERY) AS c,
        (ANOTHER VERY LONG AND COMPLICATED SUBQUERY) AS d
        FROM table
    ) AS T1
WHERE c AND d

您也可以使用CTE。

执行此操作

PostgreSQL：在WHERE子句中使用子查询缩写（'AS'）

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