仅计算符合Microsoft Access上SQL中某些条件的数据

Question

我在微软访问中有1个表，其中包含学生信息（包括性别和成绩）。我试图使用SQL视图来计算每个年级中男性和女性的数量。现在，这就是我所拥有的。

SELECT 
StudDetails.CurrClass as 'class', 
Count(StudeDetails.sex) WHERE (StudDetails.sex="M" AND StudDetails.CurrClass='class') AS 'malecount', Count (StudeDetails.sex) WHERE (StudDetails.sex="F"AND StudDetails.CurrClass='class') AS 'femalecount'
FROM StudDetails
GROUP BY StudDetails.CurrClass;

我知道这非常糟糕，但我是SQL的新手。我尝试使用谷歌搜索，但我不理解答案或不能应用它们。

Answer 1

给出表格中的两个字段 - Class 和 Gender

左侧的表格将使用此SQL显示右侧显示的结果：

SELECT      Class
            , Sex
            , COUNT(Sex) AS CountOfGender
FROM        StudDetails
GROUP BY    Class, Sex  

这里唯一的缺点是，如果班级中没有某种性别，它就不会显示0 - 它只是不会显示该性别。

+-------+--------+  +-------+--------+---------------+
| Class | Sex    |  | Class | Sex    | CountOfSex    |
+-------+--------+  +-------+--------+---------------+
|   A   |    M   |  |   A   |    F   |       2       |
+-------+--------+  +-------+--------+---------------+
|   B   |    M   |  |   A   |    M   |       3       |
+-------+--------+  +-------+--------+---------------+
|   C   |    F   |  |   B   |    M   |       1       |
+-------+--------+  +-------+--------+---------------+
|   A   |    F   |  |   C   |    F   |       1       |
+-------+--------+  +-------+--------+---------------+
|   A   |    M   |  |   D   |    M   |       2       |
+-------+--------+  +-------+--------+---------------+
|   A   |    M   |  
+-------+--------+  
|   D   |    M   |  
+-------+--------+ 
|   D   |    M   |  
+-------+--------+ 
|   A   |    F   | 
+-------+--------+    

修改 让男性和女性女性在单独的字段中并包含0，然后您可以只是交叉标记上面的查询：

TRANSFORM NZ(Sum(CountOfSex),0) AS CountOfGender
SELECT Class
FROM (
        SELECT      Class
                    , Sex
                    , COUNT(Sex) AS CountOfSex
        FROM        StudDetails
        GROUP BY    Class, Sex
      )
GROUP BY Class
PIVOT Sex  

+-------+---+---+
| Class | F | M |
+-------+---+---+
|   A   | 2 | 3 |
+-------+---+---+
|   B   | 0 | 1 |
+-------+---+---+
|   C   | 1 | 0 |
+-------+---+---+
|   D   | 0 | 2 |
+-------+---+---+

再次编辑：此方法的优点在于有条件地计算男性和＆amp;女性（IIF sex='M'.. etc）是指如果有人决定他们不想确定为男性或女性，那么它将很乐意列出您能想到的任何其他性别。

+-------+---+---+---+
| Class | F | M | Z |
+-------+---+---+---+
|   A   | 2 | 3 | 0 |
+-------+---+---+---+
|   B   | 0 | 1 | 0 |
+-------+---+---+---+
|   C   | 1 | 0 | 0 |
+-------+---+---+---+
|   D   | 0 | 2 | 1 |
+-------+---+---+---+

Answer 2

您无法以WHERE的方式使用IIF。您正在寻找Count进行比较。

由于Sum相当不灵活，因此使用SELECT StudDetails.CurrClass as 'class', Sum(IIF(StudDetails.sex="M", 1, 0)) AS malecount, Sum(IIF(StudDetails.sex="M", 0, 1)) AS femalecount FROM StudDetails GROUP BY StudDetails.CurrClass; 并在比较中分配1和0更容易。

for pattern in "$@"; do
     ...
done

Answer 3

我不确定ms访问功能，所以这些可能性并不适合你，但至少应该有一个。

-- Some sample data

create table StudDetails(sex char(1),currclass varchar(10));

insert into StudDetails values
('M','ClassA'), ('M','ClassA'), ('F','ClassA'),
('F','ClassB'), ('F','ClassB'), ('F','ClassB'), ('M','ClassB'), ('F','ClassB'),
('F','ClassC'), ('F','ClassC');

-- One method

select CurrClass as "class",
       sum(case when sex='M' then 1 else 0 end) as "malecount",
       sum(case when sex='F' then 1 else 0 end) as "femalecount"
  from StudDetails
 group by CurrClass;

-- Another method

with xxx(CurrClass,malecount,femalecount) as
  (
   select CurrClass,1,0 from StudDetails where sex = 'M'
   union all
   select CurrClass,0,1 from StudDetails where sex = 'F'
  )
  select CurrClass,sum(malecount) as malecount,sum(femalecount) as femalecount
    from xxx
    group by CurrClass;

-- Yet another method

select CurrClass,sum(malecount) as malecount,sum(femalecount) as femalecount
  from (
        select CurrClass,1 as malecount,0 as femalecount from StudDetails where sex = 'M'
        union all
        select CurrClass,0 as malecount,1 as femalecount from StudDetails where sex = 'F'
       ) xxx
  group by CurrClass;