select * from TblClass select * from TblStudent --查询:显示学生姓名及对应的班级名称 select tClassName,tSName from TblClass inner join tblstudent on TblClass.tClassId=TblStudent.tSClassId --查询:学生的姓名及英语数学分数 select tSName,tEnglish,tMath from TblStudent inner join tblscore on TblStudent.tSId=TblScore.tSId ———————————————内连接———————————————— create table groups( gid int identity(1,1) primary key not null, gname nvarchar(10), gparent int ) select * from groups insert into groups values('人事部门',3) --当前表的含义:第一级分类:总部,第二级分类:分公司,第三级分类:部门 --查询部门名称 select gname from groups as department --查询公司名称 select gname from groups as company --查询部门名称及对应的公司名称 --需要从部门表和公司表连接查询 select department.gname,company.gname from groups as department inner join groups as company on department.gparent=company.gid ———————————————外连接———————————————— select * from Department select * from Employee insert into Employee(eName,eCode,edid) values('yzk',12,100) update Employee set edid=5 where edid=1 select * from Department left join Employee on department.DId=employee.edid select * from Department right join Employee on department.DId=employee.edid select * from Department full join Employee on department.DId=Employee.edid --查询所有学生(参加及未参加考试)的学生姓名、年龄、成绩,如果没有参加考试显示“缺考”,如果小于60分显示不及格 use ItCastCn select TblStudent.tSName, isnull(cast(TblScore.tEnglish as varchar(10)),'缺考'), isnull(cast(TblScore.tMath as varchar(10)),'缺考') from tblstudent left join TblScore on TblStudent.tSId=TblScore.tSId select * from TblStudent insert into TblStudent(tSName,tSGender,tSClassId) values('yzk','男',3)
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