Question

我建立了一个数据库，将我所有的头痛和偏头痛追踪数据输入。我提出了一些问题，这些查询显示了某一年内每月头痛严重程度不同的情况。我有一个问题，每个月都会头疼，另一个在一定严重程度下会头痛，最后一个会在一定程度上头疼。 I＆＃39; m在数据库中使用了两列：HeadacheDate和Severity。我想做一个将以下列作为输出的查询：

Month, Count of All Headaches, Count of Headaches under 6 Severity, 
Count of Headaches Over 5 Severity

我做了一个联合查询，它接受了3个查询，并提供了我想要的数据，但我无法弄清楚如何进行查询以移动数据以给我列格式我想要。

以下是我的工会查询：

SELECT 
    DateName(month, DateAdd(month, MONTH(HeadacheDate), -1)) AS 
HeadacheMonth, 
    COUNT(Severity) as SeverityCount 
FROM 
    Headaches
WHERE 
    Severity > 0 AND YEAR(HeadacheDate) = 2013
GROUP BY 
    MONTH(HeadacheDate)

UNION

SELECT 
    DateName(month, DateAdd(month, MONTH(HeadacheDate), -1)) AS HeadacheMonth, 
    COUNT(Severity) as SeverityCount 
FROM 
    Headaches
WHERE 
    Severity > 0 AND Severity < 6 AND YEAR(HeadacheDate) = 2013
GROUP BY 
    MONTH(HeadacheDate)

UNION

SELECT 
    DateName(month, DateAdd(month, MONTH(HeadacheDate), -1)) AS HeadacheMonth, 
    COUNT(Severity) as SeverityCount 
FROM 
    Headaches
WHERE
    Severity > 5 AND YEAR(HeadacheDate) = 2013
GROUP BY 
    MONTH(HeadacheDate);

这会返回如下结果：

April   3
April   11
April   14
August  5
August  10
August  15
December    2
December    11
December    13
July    5
July    6
July    11
June    4
June    10
June    14
March   1
March   2
March   3
May 5
May 8
May 13
November    1
November    13
November    14
October 4
October 9
October 13
September   4
September   10
September   14

我想要的是：

Month, Count of All Headaches, Count of Headaches under 6 Severity, Count of Headaches Over 5 Severity

January, 20, 15, 5
February, 18, 13, 5

等等。

我还想包括其中一个计数字段为零的月份。

Answer 1

您可以使用条件分组：

SELECT 
  [HeadacheMonth]      = DATENAME(month, DateAdd(month , MONTH(HeadacheDate), -1))
 ,[SeverityCountTotal] = COUNT(CASE WHEN Severity > 0 THEN 1 END)
 ,[SeverityCount_1_5]  = COUNT(CASE WHEN Severity > 0 
                                     AND Severity < 6  THEN 1 END)
 ,[SeverityCount_6]    = COUNT(CASE WHEN Severity > 5 THEN 1 END)
FROM Headaches
WHERE YEAR(HeadacheDate) = 2013
GROUP BY MONTH(HeadacheDate);

YEAR(HeadacheDate) = 2013不是SARGable，因此如果索引退出该列，查询优化器将跳过它。您可以考虑使用：

HeadacheDate >= '2013-01-01T00:00:00' AND HeadacheDate < '2014-01-01T00:00:00'

Answer 2

SELECT Month
       ,COUNT(Severity) AS ALL
       ,SUM(CASE WHEN Severity<6 THEN 1 ELSE 0 END) AS SevUn6
       ,SUM(CASE WHEN Severity>5 THEN 1 ELSE 0 END) AS SevOv5

 FROM <table>
 GROUP BY Month

单独列中的SQL联合

2 个答案: