sql service (case when then else end ..... group by)

Posted 2020-09-07 Z&K

1.

原表: 
courseid coursename score 
------------------------------------- 
1 java 70 
2 oracle 90 
3 xml 40 
4 jsp 30 
5 servlet 80 
------------------------------------- 
为了便于阅读, 查询此表后的结果显式如下( 及格分数为60): 
courseid coursename score mark 
--------------------------------------------------- 
1 java 70 pass 
2 oracle 90 pass 
3 xml 40 fail 
4 jsp 30 fail 
5 servlet 80 pass 
--------------------------------------------------- 
写出此查询语句

 1 USE T4st
 2 
 3 GO
 4 IF(EXISTS(SELECT * FROM sysobjects WHERE name =\'courseTes\'))
 5 DROP TABLE courseTes
 6 GO
 7 
 8 CREATE TABLE courseTes
 9 (
10    courseid INT NOT NULL PRIMARY KEY IDENTITY,
11    coursename NVARCHAR(50) NOT NULL,
12    score INT NOT NULL
13 )
14 
15 INSERT dbo.courseTes
16         ( coursename, score )
17 VALUES  ( N\'java\', -- coursename - nvarchar(50)
18           N\'70\'  -- score - int
19           )
20 INSERT dbo.courseTes
21         ( coursename, score )
22 VALUES  ( N\'oracle\', -- coursename - nvarchar(50)
23           N\'90\'  -- score - int
24           )
25 INSERT dbo.courseTes
26         ( coursename, score )
27 VALUES  ( N\'xml\', -- coursename - nvarchar(50)
28           N\'40\'  -- score - int
29           )
30 INSERT dbo.courseTes
31         ( coursename, score )
32 VALUES  ( N\'jsp\', -- coursename - nvarchar(50)
33           N\'30\'  -- score - int
34           )
35 INSERT dbo.courseTes
36         ( coursename, score )
37 VALUES  ( N\'servlet\', -- coursename - nvarchar(50)
38           N\'80\'  -- score - int
39           )
40 SELECT * FROM courseTes
41 
42 SELECT t.courseid,t.coursename,t.score,
43 (
44    CASE
45    WHEN t.score > 60 THEN \'pass\'
46    ELSE \'fail\'
47    END  
48 ) 
49 AS mark
50 FROM courseTes AS t

运行结果如下：

2.

表内容：
2005-05-09 胜
2005-05-09 胜
2005-05-09 负
2005-05-09 负
2005-05-10 胜
2005-05-10 负
2005-05-10 负

如果要生成下列结果, 该如何写sql语句?

   时间          胜    负
2005-05-09  2     2
2005-05-10  1     2

SQL语句

 1 USE T4st
 2 
 3 GO
 4 IF(EXISTS(SELECT * FROM sysobjects WHERE name =\'Score\'))
 5 DROP TABLE Score
 6 GO
 7 
 8 CREATE TABLE Score
 9 (
10    TimeId NVARCHAR(50) NOT NULL,
11    SuccessOrFail NVARCHAR(50) NOT NULL,
12 )
13 
14 INSERT Score
15        (TimeId,SuccessOrFail)
16 VALUES (
17         N\'2005-05-09\',
18         N\'胜\'
19         )
20 INSERT Score
21        (TimeId,SuccessOrFail)
22 VALUES (
23         N\'2005-05-09\',
24         N\'胜\'
25         )
26 INSERT Score
27        (TimeId,SuccessOrFail)
28 VALUES (
29         N\'2005-05-09\',
30         N\'负\'
31         )
32 INSERT Score
33        (TimeId,SuccessOrFail)
34 VALUES (
35         N\'2005-05-09\',
36         N\'负\'
37         )
38 INSERT Score
39        (TimeId,SuccessOrFail)
40 VALUES (
41         N\'2005-05-10\',
42         N\'胜\'
43         )
44 INSERT Score
45        (TimeId,SuccessOrFail)
46 VALUES (
47         N\'2005-05-10\',
48         N\'负\'
49         )
50 INSERT Score
51        (TimeId,SuccessOrFail)
52 VALUES (
53         N\'2005-05-10\',
54         N\'负\'
55         )
56 
57 SELECT * FROM Score
58 
59 SELECT s.TimeId AS \'时间\',
60 SUM(
61   CASE
62   WHEN s.SuccessOrFail =\'胜\' THEN 1
63   ELSE 0
64   END
65 ) AS \'胜\',
66 SUM(
67   CASE
68   WHEN s.SuccessOrFail =\'负\' THEN 1
69   ELSE 0
70   END
71 ) AS \'负\'
72 FROM Score AS s GROUP BY s.TimeId

运行结果如下：