Question

由于我使用的是Union语句，因此我为每个单独的数据库中的每个城市返回了不同的行。我只想从每个数据库返回一行。但是如果我在我的％上使用SUM（）函数，它会大大扭曲百分比。我可以在查询中做些什么来准确地从两个表中返回百分比，并且每个城市只返回一行？

Select City, Sum([Hospital In 50 Miles]), [% Where Hospital In 50 Miles]
FROM (
    Select city, count(case when in50 = 'Yes' then hospID else null end) As   [Hospital In 50 Miles],
    CAST(COUNT(case when in50 = 'Yes' then hospID else null end)*1/Count(case when in50 is not null then in50 else null end) as decimal(10,4)) As [% Where Hospital In 50 Miles]
    from database1
    where in50 is not null
    UNION ALL
    Select city, count(case when in50 = 'Yes' then hospID else null end) As [Hospital In 50 Miles],
    CAST(COUNT(case when in50 = 'Yes' then hospID else null end)*1/Count(case when in50 is not null then in50 else null end) as decimal(10,4)) As [% Where Hospital In 50 Miles]
    from database2
    where in50 is not null
  ) as
  Group by city

Answer 1

您不能平均SUM，您必须对组件求和并对它们求平均值。像这样：

Select City, Sum([Hospital In 50 Miles]), 
Sum([Hospital In 50 Miles])/SUM([Hospitals]) AS [% Where Hospital In 50 Miles]
FROM (
    Select city, count(case when in50 = 'Yes' then hospID else null end) As   [Hospital In 50 Miles],
    CAST(Count(case when in50 is not null then in50 else null end) as decimal(10,4)) As [Hospitals]
    from database1
    where in50 is not null
    UNION ALL
    Select city, count(case when in50 = 'Yes' then hospID else null end) As [Hospital In 50 Miles],
    CAST(Count(case when in50 is not null then in50 else null end) as decimal(10,4)) As [Hospitals]
    from database2
    where in50 is not null
  ) as
  Group by city

可能需要对输出进行一些额外的格式化，但这是基本结构。

Answer 2

为什么不在每个子查询中添加一个总列，所以你有类似

的东西

SELECT  City,
        In50 = COUNT(CASE WHEN In50 = 'Yes' THEN 1 END),
        Total = COUNT(*)
FROM    Database1
WHERE   In50 IS NOT NULL
GROUP BY City

然后你的％计算只是SUM(In50) / SUM(Total)：

SELECT  City,
        In50 = SUM(In50),
        PercentIn50 = 1.0 * SUM(In50) / SUM(Total)
        Total = SUM(Total)
FROM    (
            SELECT  City,
                    In50 = COUNT(CASE WHEN In50 = 'Yes' THEN 1 END),
                    Total = COUNT(*)
            FROM    Database1
            WHERE   In50 IS NOT NULL
            GROUP BY City
            UNION ALL
            SELECT  City,
                    In50 = COUNT(CASE WHEN In50 = 'Yes' THEN 1 END),
                    Total = COUNT(*)
            FROM    Database2
            WHERE   In50 IS NOT NULL
            GROUP BY City
        ) AS t
GROUP BY City;

N.B。我已经通过可能导致查询失败的子句添加了缺少的组，并删除了冗余检查，例如COUNT(CASE WHEN In50 IS NOT NULL THEN In50 ELSE NULL END) - 这是没有必要的，因为你在where子句中已经有WHERE In50 IS NOT NULL

显示1个百分比计数

2 个答案: