sql笔记-group by 统计功能

1 --查询月销售量小于20的人员销售情况
2 SELECT C.Category,
3        SUM(c.[Count]) AS CategorySum
4 FROM   test.dbo.Category c
5        --WHERE c.Category IN ('A','C')
6 GROUP BY
7        C.Category
8 HAVING SUM(c.[Count]) < 20
9 ORDER BY
10        CategorySum
11
12 --查询每门课的最低分
13 SELECT C.Category,
14        MIN(C.[Count]) AS CategoryMinCount
15 FROM   test.dbo.Category c
16 GROUP BY
17        C.Category
18
19
20 --搜索名字相同的学生
21 SELECT s.Sname,
22        COUNT(s.Sname)
23 FROM   Stu s
24 GROUP BY
25        s.Sname
26 HAVING COUNT(s.Sname) > 1
27
28
29 --每个年龄的人数
30 SELECT
31     s.Age
32     ,COUNT(s.Age) AS AgeCount
33 FROM test.dbo.Stu s
34 GROUP BY s.Age
35
36 --年龄段统计
37 SELECT t1.AgeRange,
38        COUNT(*) AS AgeRangePeopleCount
39 FROM   (
40            SELECT Sno,
41                   CASE
42                        WHEN (age > 50) THEN 'gt100'
43                        WHEN (age > 20 AND age <= 50) THEN '20-30'
44                        WHEN (age <= 20) THEN '10-20'
45                   END AS AgeRange
46            FROM   test.dbo.Stu s
47        ) t1
48 GROUP BY
49        t1.AgeRange