教师号 星期号 是否有课
1 2 有
1 3 有
2 1 有
3 2 有`
1 2 有
写一条sql语句让你变为这样的表
教师号 星期一 星期二 星期三
1 2 1
2 1
3 1
各星期下的数字表示:对应的教师在星期几已经排的课数
数据库表信息如下
简单的SQL
select a.teacherid as 教师号,sum(a.w1) 星期一,sum(a.w2) 星期二,sum(a.w3) 星期三 from( select teacherid,case when week=1 then 1 end w1, case when week=2 then 1 end w2,case when week=3 then 1 end w3 from course) a group by teacherid
复杂的SQL
select b.teacherid,sum(w1) as 星期一,sum(w2) 星期二,sum(w3) 星期三 from ( select a.teacherid,case when a.week=1 then a.num end as w1,case when a.week=2 then a.num end as w2, case when a.week=3 then a.num end as w3 from (select teacherid,week,count(*) as num from course group by teacherid,week) a) b group by b.teacherid