/*用CASE WHEN实现sqlserver数据库的分类汇总功能*/
/*例1：统计个数*/
/*表结构
id cityid major
1 1 A
2 1 B
3 2 B
4 2 A
5 1 A
6 2 B
7 1 C
8 2 C
结果：
cityId A B C
1 2 1 1
2 1 2 1
*/
SELECT cityId,SUM(CASE WHEN major='A' THEN 1 ELSE 0 END) AS 'A',
SUM(CASE WHEN major='B' THEN 1 ELSE 0 END) AS 'B',
SUM(CASE WHEN major='C' THEN 1 ELSE 0 END) AS 'C'
FROM TestCase1 GROUP BY cityId
/*例1：统计总和数*/
/*表结构
Id cityId catalogId Num
1 1 A 3
2 1 B 5
3 2 A 8
4 2 B 2
5 1 A 1
6 1 B 2
7 2 C 3
8 2 C 4
9 1 C 1
10 1 C 2
11 2 A 3
12 2 B 4
结果：
cityId A B C 总计
1 4 7 3 14
2 11 6 7 24
*/
SELECT cityId,SUM(CASE WHEN catalog='A' THEN num ELSE 0 END) AS 'A', SUM(CASE WHEN catalog='B' THEN num ELSE 0 END) AS 'B', SUM(CASE WHEN catalog='C' THEN num ELSE 0 END) AS 'C', SUM(Num) as '总计' FROM TestCase2 GROUP BY cityId
