SQL编程

1、case…when…then的使用

create table score(
name varchar(30) not null,
subject varchar(30) not null,
score tinyint unsigned not null
)engine = myisam default charset=utf8;

insert into score values
('张三','语文',90),
('张三','数学',90),
('张三','英语',90),
('李四','语文',80),
('李四','数学',80),
('李四','英语',80),
('王五','语文',70),
('王五','数学',70),
('王五','英语',70);

查询每位学员各科成绩多少分，以及总分

select name,
    sum(case subject when '语文' then score else 0 end) as '语文',
    sum(case subject when '数学' then score else 0 end) as '数学',
    sum(case subject when '英语' then score else 0 end) as '英语', 
    sum(score) as '总分'
from score group by name