sql语句的联合查询(join 用法)
2004-11-10 12:29
811 查看
student
no,name,classid,
1, zdy,2,
2,huz,2,
3,yxx,2,
4,sss,1,
class
classid,classname,
2,y2002,
3,y2003,
1 .select * from student , class where student.classid=class.classid
no,name,classid,classid,classname,
1,zdy,2,2,y2002,
2,huz,2,2,y2002,
3,yxx,2,2,y2002,
2.select * from student left join class on student.classid=class.classid
no,name,classid,classid,classname,
1,zdy,2,2,y2002,
2,huz,2,2,y2002,
3,yxx,2,2,y2002,
4,sss,1, , ,
3.select * from student inner join class on student.classid=class.classid
no,name,classid,classid,classname,
1,zdy,2,2,y2002,
2,huz,2,2,y2002,
3,yxx,2,2,y2002,
结果同1
4.select * from student right join class on student.classid=class.classid
no,name,classid,classid,classname,
1,zdy,2,2,y2002,
2,huz,2,2,y2002,
3,yxx,2,2,y2002,
, , , 3,y2003,
no,name,classid,
1, zdy,2,
2,huz,2,
3,yxx,2,
4,sss,1,
class
classid,classname,
2,y2002,
3,y2003,
1 .select * from student , class where student.classid=class.classid
no,name,classid,classid,classname,
1,zdy,2,2,y2002,
2,huz,2,2,y2002,
3,yxx,2,2,y2002,
2.select * from student left join class on student.classid=class.classid
no,name,classid,classid,classname,
1,zdy,2,2,y2002,
2,huz,2,2,y2002,
3,yxx,2,2,y2002,
4,sss,1, , ,
3.select * from student inner join class on student.classid=class.classid
no,name,classid,classid,classname,
1,zdy,2,2,y2002,
2,huz,2,2,y2002,
3,yxx,2,2,y2002,
结果同1
4.select * from student right join class on student.classid=class.classid
no,name,classid,classid,classname,
1,zdy,2,2,y2002,
2,huz,2,2,y2002,
3,yxx,2,2,y2002,
, , , 3,y2003,
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