MySQL中Case When用法及说明

use hiveDemo;
CREATE TABLE `course` (
  `id` int,
  `sid` int ,
  `course` string,
  `score` int 
) ;

// 字段解释：id, 学号， 课程， 成绩
INSERT INTO `course` VALUES (1, 1, 'yuwen', 43);
INSERT INTO `course` VALUES (2, 1, 'shuxue', 55);
INSERT INTO `course` VALUES (3, 2, 'yuwen', 77);
INSERT INTO `course` VALUES (4, 2, 'shuxue', 88);
INSERT INTO `course` VALUES (5, 3, 'yuwen', 98);
INSERT INTO `course` VALUES (6, 3, 'shuxue', 65);

create view tmp_course_view as
select sid, case course when "shuxue" then score else 0 end  as shuxue,  
case course when "yuwen" then score else 0 end  as yuwen from course;  
 
select * from tmp_course_view;

create view tmp_course_view1 as
select aa.sid, max(aa.shuxue) as shuxue, max(aa.yuwen) as yuwen from tmp_course_view aa group by sid;  
 
select * from tmp_course_view1;

select * from tmp_course_view1 where shuxue > yuwen;

update table  
set 字段1=case     
    when 条件1 then 值1       
    when 条件2 then 值2      
    else 值3      
    end     
where    …… 

select 字段1, 字段2,       
    case 字段3     
    when 值1 then 新值       
    when 值2 then 新值      
    end as 重新命名字段3的名字       
from table      
where ……      
order by ……  

sql 中 case when 语法在这里添加日志标题 - 钱途无梁 - Notebook of 钱途无梁SELECT <myColumnSpec> = 
sql 中 case when 语法在这里添加日志标题 - 钱途无梁 - Notebook of 钱途无梁CASE 
sql 中 case when 语法在这里添加日志标题 - 钱途无梁 - Notebook of 钱途无梁WHEN <A> THEN <somethingA> 
sql 中 case when 语法在这里添加日志标题 - 钱途无梁 - Notebook of 钱途无梁WHEN <B> THEN <somethingB> 
sql 中 case when 语法在这里添加日志标题 - 钱途无梁 - Notebook of 钱途无梁ELSE <somethingE> 
sql 中 case when 语法在这里添加日志标题 - 钱途无梁 - Notebook of 钱途无梁END