标签：style blog color 使用 io 数据 2014 cti
话说好久没写Sql了，结果和其他小组的同事写Sql的时候遭到鄙视了，看来Sql是永远不能丢的，有时间就要温习一下。
创建3张表：
Rel_SutAndCourse，T_Course，T_Stu
为3张表填充数据：
----Student begin transaction insert T_Stu(StuCode,StuName,Sex) values (‘Stu001‘,‘zhang chu chu‘,1) insert T_Stu(StuCode,StuName,Sex) values (‘Stu002‘,‘li xiao long‘,1) insert T_Stu(StuCode,StuName,Sex) values (‘Stu003‘,‘cheng long‘,1) insert T_Stu(StuCode,StuName,Sex) values (‘Stu004‘,‘liu shi shi‘,0) insert T_Stu(StuCode,StuName,Sex) values (‘Stu005‘,‘yang mi‘,0) insert T_Stu(StuCode,StuName,Sex) values (‘Stu006‘,‘a sa‘,0) insert T_Stu(StuCode,StuName,Sex) values (‘Stu007‘,‘a jiao‘,0) commit transaction
----Course select * from T_Course begin transaction insert T_Course(CourseCode,CourseName) values (‘course01‘,‘yu wen‘) insert T_Course(CourseCode,CourseName) values (‘course02‘,‘shu xue‘) insert T_Course(CourseCode,CourseName) values (‘course03‘,‘ying yu‘) insert T_Course(CourseCode,CourseName) values (‘course04‘,‘ti yu‘) commit transaction
----Relation select * from Rel_SutAndCourse begin transaction insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (1,1,GETDATE()) insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (2,1,GETDATE()) insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (3,2,GETDATE()) insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (3,3,GETDATE()) insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (4,1,GETDATE()) insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (4,2,GETDATE()) insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (4,3,GETDATE()) insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (4,4,GETDATE()) insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (3,1,GETDATE()) insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (5,1,GETDATE()) insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (6,1,GETDATE()) insert Rel_SutAndCourse(StuId,CourseId,CreateTime) values (7,1,GETDATE()) commit transaction
然后虚拟出3个需求：
--查询出每门课程选课的学生数 select CourseId,count(*) as SutCount from Rel_SutAndCourse group by CourseId
--查询每个学生选的课的数目 select StuId,count(*) as SutCount from Rel_SutAndCourse group by StuId
--查询男女同学选课的数量 select stu.sex,Count(distinct rel.stuid) from Rel_SutAndCourse rel inner join T_Stu stu on rel.StuId=stu.Id group by stu.sex
--以2014-08-03 19:55为时间分割点，查询哪些同学在时间点之前选课，哪些在时间点之后选了课 select * from Rel_SutAndCourse select stu.Id,stu.StuName from T_Stu stu join Rel_SutAndCourse rel on stu.id=rel.StuId where rel.Id<=( select max(rel.Id) from Rel_SutAndCourse rel where rel.CreateTime<‘2014-08-03 19:55‘ ) group by stu.Id,stu.StuName select stu.Id,stu.StuName from T_Stu stu join Rel_SutAndCourse rel on stu.id=rel.StuId where rel.Id>=( select min(rel.Id) from Rel_SutAndCourse rel where rel.CreateTime>‘2014-08-03 19:55‘ ) group by stu.Id,stu.StuName
其实就是个简单的分组，一直认为自己的Sql是写的最烂的，看来必须加强啊，争取每次学一些。
标签：style blog color 使用 io 数据 2014 cti
原文地址：http://www.cnblogs.com/xiguain/p/3889808.html
