Postgresql 在复杂查询上生成有序序列秩

我试图在查询的输出中创建一个隐式秩。问题似乎是在计算

worth

之前运行了

row\u number（）

SELECT 
    firstname,
    lastname,
    personid,
    year,
    (
        SELECT COALESCE(SUM(thevalue),0) 
        FROM assets WHERE personidref = w.personid AND year = w.year
    ) AS assets ,
    (
        SELECT COALESCE(SUM(amount),0) 
        FROM liabilities WHERE personidref = w.personid AND year = w.year
    ) AS liabilities,
    (
        (SELECT COALESCE(SUM(thevalue),0) 
         FROM assets 
         WHERE personidref = w.personid AND year = w.year) 
        - 
        (SELECT COALESCE(SUM(amount),0) 
         FROM liabilities 
         WHERE personidref = w.personid AND year = w.year)
    ) as worth,
    row_number() over(ORDER BY w.worth) as rank 
FROM members w 
WHERE year = 2012 
ORDER BY worth DESC LIMIT 2;

结果是我得到了这个：

| firstname | lastname | personid | year | assets | liabilities | worth | rank |
+-----------+----------+----------+------+--------+-------------+-------+------+
| foo       | bar      | 234      | 2012 | 30000  | 20          | 29980 | 32   |
| foo2      | bar2     | 5234     | 2012 | 30000  | 100         | 29900 | 69   |

而不是期望的输出：

| firstname | lastname | personid | year | assets | liabilities | worth | rank |
+-----------+----------+----------+------+--------+-------------+-------+------+
| foo       | bar      | 234      | 2012 | 30000  | 20          | 29980 | 1    |
| foo2      | bar2     | 5234     | 2012 | 30000  | 100         | 29900 | 2    |

有没有办法预运行此查询并按排名第一进行预排序？
将行数加倍（）如何

没有样本数据很难确定，但如果你想要排名

或

?

这是我认为你可能想要做的。未测试，因为没有样本数据或可用于测试，但：

SELECT
    *,
    dense_rank() OVER (ORDER BY worth)
FROM
(
    SELECT
        *,
        assets - liabilities AS worth
    FROM
    (
        SELECT 
            firstname,
            lastname,
            personid,
            year,
            (
                SELECT COALESCE(SUM(a.thevalue),0) 
                FROM assets a WHERE a.personidref = w.personid AND a.year = w.year
            ) AS assets ,
            (
                SELECT COALESCE(SUM(l.amount),0) 
                FROM liabilities l WHERE l.personidref = w.personid AND l.year = w.year
            ) AS liabilities
        FROM members w
        WHERE year = 2012
    ) AS a_and_l
) AS net_worths
ORDER BY worth DESC
LIMIT 2;

似乎没有任何更多的性能影响（比20
COALESCE
s更多），这非常有效！将您的查询重新格式化为易读。您的第一个
资产
查询是否缺少一个年度筛选器？顺便说一句，为了获得更好的性能，您可能实际上需要另一个级别的子查询，因此您可以
按值描述限制2排序
，然后才可以
密集排列（）
匹配行。在上面的例子中，您可能会在所有行上进行
密集排序（）
，然后扔掉大部分。
rank() over(ORDER BY w.worth) as rank 

dense_rank() over(ORDER BY w.worth) as rank 

SELECT
    *,
    dense_rank() OVER (ORDER BY worth)
FROM
(
    SELECT
        *,
        assets - liabilities AS worth
    FROM
    (
        SELECT 
            firstname,
            lastname,
            personid,
            year,
            (
                SELECT COALESCE(SUM(a.thevalue),0) 
                FROM assets a WHERE a.personidref = w.personid AND a.year = w.year
            ) AS assets ,
            (
                SELECT COALESCE(SUM(l.amount),0) 
                FROM liabilities l WHERE l.personidref = w.personid AND l.year = w.year
            ) AS liabilities
        FROM members w
        WHERE year = 2012
    ) AS a_and_l
) AS net_worths
ORDER BY worth DESC
LIMIT 2;