目录[-]
一、行转列
1.1、初始测试数据
表结构：TEST_TB_GRADE
Sql代码:
1 create table TEST_TB_GRADE 2 ( 3 ID NUMBER(10) not null, 4 USER_NAME VARCHAR2(20 CHAR), 5 COURSE VARCHAR2(20 CHAR), 6 SCORE FLOAT 7 )
初始数据如下图：
1.2、 如果需要实现如下的查询效果图：
这就是最常见的行转列，主要原理是利用decode函数、聚集函数(sum)，结合group by分组实现的，具体的sql如下：
Sql代码:
1 select t.user_name, 2 sum(decode(t.course, ‘语文‘, score,null)) as CHINESE, 3 sum(decode(t.course, ‘数学‘, score,null)) as MATH, 4 sum(decode(t.course, ‘英语‘, score,null)) as ENGLISH 5 from test_tb_grade t 6 group by t.user_name 7 order by t.user_name
1.3、延伸
如果要实现对各门功课的不同分数段进行统计，效果图如下：
具体的实现sql如下：
Sql代码:
1 select t2.SCORE_GP, 2 sum(decode(t2.course, ‘语文‘, COUNTNUM,null)) as CHINESE, 3 sum(decode(t2.course, ‘数学‘, COUNTNUM,null)) as MATH, 4 sum(decode(t2.course, ‘英语‘, COUNTNUM,null)) as ENGLISH 5 from ( 6 select t.course, 7 case when t.score <60 then ‘00-60‘ 8 when t.score >=60 and t.score <80 then ‘60-80‘ 9 when t.score >=80 then ‘80-100‘ end as SCORE_GP, 10 count(t.score) as COUNTNUM 11 FROM test_tb_grade t 12 group by t.course, 13 case when t.score <60 then ‘00-60‘ 14 when t.score >=60 and t.score <80 then ‘60-80‘ 15 when t.score >=80 then ‘80-100‘ end 16 order by t.course ) t2 17 group by t2.SCORE_GP 18 order by t2.SCORE_GP
二、列转行
1.1、初始测试数据
表结构： TEST_TB_GRADE2Sql代码:
1 create table TEST_TB_GRADE2 2 ( 3 ID NUMBER(10) not null, 4 USER_NAME VARCHAR2(20 CHAR), 5 CN_SCORE FLOAT, 6 MATH_SCORE FLOAT, 7 EN_SCORE FLOAT 8 )
初始数据如下图：
1.2、 如果需要实现如下的查询效果图：
这就是最常见的列转行，主要原理是利用SQL里面的union，具体的sql语句如下：
Sql代码:
1 select user_name, ‘CN_SCORE‘ COURSE , CN_SCORE as SCORE from test_tb_grade2 2 union 3 select user_name, ‘MATH_SCORE‘ COURSE, MATH_SCORE as SCORE from test_tb_grade2 4 union 5 select user_name, ‘EN_SCORE‘ COURSE, EN_SCORE as SCORE from test_tb_grade2 6 order by user_name,COURSE
也可以利用【insert all into ... select】来实现，首先需要先建一个表TEST_TB_GRADE3：
Sql代码:1 create table TEST_TB_GRADE3 2 ( 3 USER_NAME VARCHAR2(20 CHAR), 4 COURSE VARCHAR2(20 CHAR), 5 SCORE FLOAT 6 )
再执行下面的sql：
Sql代码:
1 insert all 2 into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, ‘语文‘, CN_SCORE) 3 into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, ‘数学‘, MATH_SCORE) 4 into test_tb_grade3(USER_NAME,COURSE,SCORE) values(user_name, ‘英语‘, EN_SCORE) 5 select user_name, CN_SCORE, MATH_SCORE, EN_SCORE from test_tb_grade2; 6 commit;