oracle 中分类统计:case when..then..else..end用法_oracle case when then else 统计

create table SC(SId varchar2(10),CId varchar2(10),score decimal(18,1));
insert into SC values('01' , '01' , 80);
insert into SC values('01' , '02' , 90);
insert into SC values('01' , '03' , 99);
insert into SC values('02' , '01' , 70);
insert into SC values('02' , '02' , 60);
insert into SC values('02' , '03' , 80);
insert into SC values('03' , '01' , 80);
insert into SC values('03' , '02' , 80);
insert into SC values('03' , '03' , 80);
insert into SC values('04' , '01' , 50);
insert into SC values('04' , '02' , 30);
insert into SC values('04' , '03' , 20);
insert into SC values('05' , '01' , 76);
insert into SC values('05' , '02' , 87);
insert into SC values('06' , '01' , 31);
insert into SC values('06' , '03' , 34);
insert into SC values('07' , '02' , 89);
insert into SC values('07' , '03' , 98);

1.SELECT SID ,sum(case  when  CID='01' then '1'  else '0' end) ,avg(sid) FROM SC group by SID order by SID

2.SELECT SID ,sum(case  when  CID='01' then score  else 0 end) ,avg(sid) FROM SC group by SID order by SID

在使用case when 条件1 then 结果1 else 结果2 end 时 要注意返回结果的数据类型要一致。

SELECT SID ,sum(case  when  CID='01' then score  else 0 end) as "语文" ,sum(case  when  CID='02' then score  else 0 end) as "数学" ,sum(case  when  CID='03' then score  else 0 end) as "英语" ， cast（avg(score) as number(10,2)） FROM SC group by SID order by avg(score)