记一次行转列-sql

Posted 2020-11-09 zuoruining

1. 创建测试表

   CREATE TABLE  ZLTEST (
     TEACHER_NO VARCHAR(10),
     WEEK_NO VARCHAR(10),
     COURSE VARCHAR(30)
   )

2. 插入数据

   INSERT INTO ZLTEST VALUES (1,1,'有')
   INSERT INTO ZLTEST VALUES (2,2,'有')
   INSERT INTO ZLTEST VALUES (1,3,'有')
   INSERT INTO ZLTEST VALUES (2,4,'有')
   INSERT INTO ZLTEST VALUES (1,5,'有')
   INSERT INTO ZLTEST VALUES (2,1,'有')

   
   3、case when实现：

   SELECT ZLTEST.TEACHER_NO AS 老师编号,
     max(CASE WHEN WEEK_NO =1 THEN COURSE ELSE '' END ) as 星期一,
     max(CASE WHEN WEEK_NO = 2 THEN COURSE ELSE '' END ) AS 星期二,
     max(CASE WHEN WEEK_NO = 3 THEN COURSE ELSE '' END ) AS 星期三,
     max(CASE WHEN WEEK_NO = 4 THEN COURSE ELSE '' END ) AS 星期四,
     max(CASE WHEN WEEK_NO = 5 THEN COURSE ELSE ''  END ) AS 星期五
   FROM ZLTEST GROUP BY ZLTEST.TEACHER_NO

   

3. ORACLE 数据库可以用decode函数实现：

   SELECT ZLTEST.TEACHER_NO AS 老师编号,
     max(decode(t.WEEK_NO,'1',COURSE)) as 星期一,
     max(decode(t.WEEK_NO,'2',COURSE)) as 星期二,
     max(decode(t.WEEK_NO,'3',COURSE)) AS 星期三,
     max(decode(t.WEEK_NO,'4',COURSE)) AS 星期四,
     max(decode(t.WEEK_NO,)'5',COURSE) AS 星期五
   FROM ZLTEST
   GROUP BY  ZLTEST.TEACHER_NO
   ORDER BY ZLTEST.TEACHER_NO