在SQL中划分两个查询然后分组

Question

我正在寻找新帐户和所有帐户之间的费率变化，我在下面列出了两个查询。 我需要通过AllAccounts划分NewAccounts，在同一个查询中获取该百分比并按城镇分组。 谢谢

SELECT DISTINCT  Count(NewAccounts), Town
FROM   (SELECT Stuff)
WHERE   (Newaccounts)
Group By Town
;
SELECT DISTINCT  Count(AllAccounts), Town
FROM   (SELECT DifferentSTUFF)
WHERE   (AllAccounts)
Group By Town

Answer 1

您需要将查询重写为子查询并将它们连接在一起：

SELECT  CAST(na.NewAccounts AS FLOAT) / aa.AllAccounts
FROM    (   SELECT Count(NewAccounts) AS NewAccounts, Town
            FROM   (SELECT Stuff)
            WHERE   (Newaccounts)
            GROUP BY Town
        ) na
        INNER JOIN
        (   SELECT Count(AllAccounts) AS AllAccounts, Town
            FROM   (SELECT DifferentSTUFF)
            WHERE   (AllAccounts)
            GROUP BY Town
        ) aa
            ON aa.Town = na.Town;

我从两个查询中删除了DISTINCT ，因为它是多余的。 在NewAccounts上浮动的NewAccounts转换是为了避免将结果整数除法隐式转换回整数。

根据每个查询中的数据可用性，您可能需要稍微改变一下，即如果您不会总是在城镇的新帐户中有结果，那么最好将其写为：

SELECT  CAST(COALESCE(na.NewAccounts, 0) AS FLOAT) / aa.AllAccounts
FROM    
        (   SELECT Count(AllAccounts) AS AllAccounts, Town
            FROM   (SELECT DifferentSTUFF)
            WHERE   (AllAccounts)
            GROUP BY Town
        ) aa
        LEFT JOIN
        (   SELECT Count(NewAccounts) AS NewAccounts, Town
            FROM   (SELECT Stuff)
            WHERE   (Newaccounts)
            GROUP BY Town
        ) na
            ON aa.Town = na.Town