什么是部署php网站,西红门做网站,网站建设博采,不断改进网站建设Oracle#xff1b;有2个表如下#xff1b; 执行下图选中的左连接#xff1b; 左表10条记录#xff0c;右表3条记录#xff0c;结果是10条记录#xff1b;
执行下图的左连接#xff0c; 老师表为左表#xff0c;学生表为右表#xff0c;结果会显示每个老师#xff0c…Oracle有2个表如下 执行下图选中的左连接 左表10条记录右表3条记录结果是10条记录
执行下图的左连接 老师表为左表学生表为右表结果会显示每个老师这里结果是11行我映象中没写过这样的都用的前面一种左连接
然后看一下全连接 结果是11行
交换一下左右表 结果也是11行 Oracle支持全连接SqlServer应支持根据网上资料MySQL不支持全连接
Oracle如下写将报错
select * from students as s left join teachers as t on s.Tid t.Tid;
select * from students;
select * from teachers;select * from students s
left join teachers t
on s.Tid t.Tid;select * from teachers t
left join students s
on t.Tid s.Tid;select * from students s
full join teachers t
on s.Tid t.Tid;select * from teachers t
full join students s
on t.Tid s.Tid;
