1. select 班级 ,max(平均分) as maxavg from (select 班级,avg(成绩) as 平均分 from BB,AA where AA.学号 = BB.学号 and BB.学科名称 = '数学' and BB.学期 ='3' group by AA.班级 ) as a group by 班级 union all select 班级 ,min(平均分) as maxavg from (select 班级,avg(成绩) as 平均分 from BB,AA where AA.学号 = BB.学号 and BB.学科名称 = '数学' and BB.学期 ='3' group by AA.班级 ) as a group by 班级 2.select count(*) form AA where datediff(year,出生日期,getdate())<30
1. select aa.班级,avg(bb.成绩) as [平均分] from aa,bb where aa.学号=bb.学号 and bb.学科名称='数学' and 学期='第三学期' group by aa.班级 order by avg(bb.成绩)2. select count(*) form AA where datediff(year,出生日期,getdate())<30
2.应该这样哦 select count(*) from AA where datediff(dd,dateadd(yy,30,出生日期),getdate())>=0
select count(*) from AA where datediff(dd,dateadd(yy,30,出生日期),getdate())<0
select 班级 ,max(平均分) as maxavg
from
(select 班级,avg(成绩) as 平均分
from BB,AA
where AA.学号 = BB.学号
and BB.学科名称 = '数学'
and BB.学期 ='3'
group by AA.班级 ) as a
group by 班级
union all
select 班级 ,min(平均分) as maxavg
from
(select 班级,avg(成绩) as 平均分
from BB,AA
where AA.学号 = BB.学号
and BB.学科名称 = '数学'
and BB.学期 ='3'
group by AA.班级 ) as a
group by 班级
2.select count(*) form AA where datediff(year,出生日期,getdate())<30
select aa.班级,avg(bb.成绩) as [平均分] from aa,bb where aa.学号=bb.学号 and bb.学科名称='数学' and 学期='第三学期' group by aa.班级 order by avg(bb.成绩)2.
select count(*) form AA where datediff(year,出生日期,getdate())<30
select count(*) from AA where datediff(dd,dateadd(yy,30,出生日期),getdate())>=0