分组查询不显示所有行

Question

我有一个表tblPersonaldata和tblStudentsadmitted

。

tblPersonalData

UID  Name Gender
------------------------ 
 E1   xyz   M
 E2   pqr   M
 E3   mno   M

tblStudentsadmitted

UID   Status  Stage
----------------------
E1     Y        1
E2     Y        2
E3     Y        1

现在我想要的数据是这样的：

Gender  Stage1   Stage2
 M        2       1

但在这种情况下，我无法获取女性的数据。即使数据为空，我也希望获得女性的数据。

我已经尝试过以下方法：

select 
    case 
        when gender='M' then 'Male' 
        when gender='F' then 'Female' 
    end as Gender,
    sum(case when Stage=1 then 1 else 0) end as Stage1,
    sum(case when Stage=2 then 1 else 0) end as Stage2
from  tblPersonaldata A inner join 
      tblStudentsadmitted B on A.UID=B.UID 
where B.Status='Y'
group by Gender

- user1274646

---

你的样本表是你所有的信息吗？因为你没有任何女性数据？ - CathalMF

Answer 1

SELECT  CASE WHEN a.Gender = 'M' THEN 'Male' ELSE 'FEMALE' END Gender,
        SUM(CASE WHEN Stage = 1 THEN 1 ELSE 0 END) Stage1,
        SUM(CASE WHEN Stage = 2 THEN 1 ELSE 0 END) Stage2
FROM    personal a
        LEFT JOIN studentadmitted b
            ON a.UID = b.UID AND b.Status = 'Y'
GROUP   BY a.Gender

• SQLFiddle演示

SELECT  CASE WHEN c.Gender = 'M' THEN 'Male' ELSE 'Female' END Gender,
        SUM(CASE WHEN Stage = 1 THEN 1 ELSE 0 END) Stage1,
        SUM(CASE WHEN Stage = 2 THEN 1 ELSE 0 END) Stage2
FROM    (SELECT 'F' Gender UNION SELECT 'M' Gender) c
        LEFT JOIN personal a
            ON a.Gender = c.Gender
        LEFT JOIN studentadmitted b
            ON a.UID = b.UID AND b.Status = 'Y'
GROUP   BY c.Gender

• SQLFiddle演示

输出结果

╔════════╦════════╦════════╗
║ GENDER ║ STAGE1 ║ STAGE2 ║
╠════════╬════════╬════════╣
║ Female ║      0 ║      0 ║
║ Male   ║      2 ║      1 ║
╚════════╩════════╩════════╝

- John Woo

---

@user1274646，您介意发表您的查询吗？也许您错过了什么。 - John Woo

@JW 是的，我明白了，查询正在运行，但我仍然没有得到女性行。 - user1274646

你能发一下查询吗？:D 看看这个fiddle，它正常工作吗？http://www.sqlfiddle.com/#!3/673c3/10 - John Woo

Answer 2

在 SQL Server 中，您可以使用 PIVOT 函数生成结果。

select gender,
  Stage1, 
  Stage2
from
(
  select 
    c.gender,
    'Stage'+cast(stage as varchar(10)) Stage
  from (values ('F'),('M')) c (gender)
  left join tblpersonaldata p
    on c.gender = p.gender
  left join tblStudentsadmitted s
    on p.uid = s.uid
    and s.Status='Y'
)src
pivot
(
  count(stage)
  for stage in (Stage1, Stage2)
) piv

请查看带演示的SQL Fiddle。

由于您使用的是SQL Server 2008，因此此查询使用VALUES生成要在最终结果集中显示的性别列表。

from (values ('F'),('M')) c (gender)

通过在其他表上使用 LEFT JOIN，最终结果将返回M和F值的行。

这也可以使用 UNION ALL 来生成性别列表：

select gender,
  Stage1, 
  Stage2
from
(
  select 
    c.gender,
    'Stage'+cast(stage as varchar(10)) Stage
  from 
  (
    select 'F' gender union all
    select 'M' gender
  ) c
  left join tblpersonaldata p
    on c.gender = p.gender
  left join tblStudentsadmitted s
    on p.uid = s.uid
    and s.Status='Y'
)src
pivot
(
  count(stage)
  for stage in (Stage1, Stage2)
) piv

请查看带有演示的SQL Fiddle

两者的结果都是：

| GENDER | STAGE1 | STAGE2 |
----------------------------
|      F |      0 |      0 |
|      M |      2 |      1 |

- Taryn

Answer 3

这也是可行的。使用左连接与一个新表（一个包含性别M和F两个记录的表）。

Fiddle演示

select  t.g Gender,
        isnull(sum(case when Stage = 1 then 1 end),0) Stage1,
        isnull(sum(case when Stage = 2 then 1 end),0) Stage2
from    (values ('M'),('F')) t(g) 
            left join personal a on t.g = a.gender
            left join studentadmitted b on a.uid = b.uid and b.Status = 'Y'
group by t.g
order by t.g

| GENDER | STAGE1 | STAGE2 |
----------------------------
|      F |      0 |      0 |
|      M |      2 |      1 |

- Kaf

Answer 4

选择 GENDER, 0 AS 'STAGE 0', 1 AS 'STAGE 1', 2 AS 'STAGE 2'
从 ( SELECT P.ID, GENDER,CASE WHEN STAGE IS NULL THEN 0 ELSE STAGE END STAGE FROM tblPersonaldata P LEFT JOIN tblStudentsadmitted S ON P.UID = S.UID ) AS A PIVOT ( COUNT (ID) FOR STAGE IN ([0],[1],[2]) )P

- user2160561