a left join b 与 b right join a 是否一样他们的含义是什么

a left join b 与 b right join a 是否一样他们的含义是什么 left join 与where 两种关联区别例如：select * from a left join b on a.no=b.no与语句 select * from a,b where a.no=b.no的区别,那个性能更优 sql中left join from 多个表怎么写select * from a,b,c,d LEFT JOIN e on e.id=a.id left join f on f.id=c.id现在这句是错的,怎么写才正确 oracle语句join和（+）的用法oracle使用 left join或者right join,比如select A.*,B.* from A left join B on A.*=B.*.如果用（+）该怎么写,join语句后面定义一定要用on吗. left outer join on中 on 的后面可以加几个等式?如 a left outer join b on a.x=b.x and a.y=b.y 可以吗? 大量的left join 怎么优化select a.id,a.num,b.num,b.pcs,c.num,c.pcs,d.num,d.pcs,e.num,e.pcs,a.x,a.y from a left join b.id=a.id and b.time=a.timeleft join c.id=a.id and b.time=a.timeleft join d.id=a.id and b.time=a.timeleft join e.id=a.id and b.t left join 和where的问题在一个已经用了from a,b 方法做了联合 还能继续用left join select a.my_name,b.my_name,c.my_name from a,b left join c on c.nid=a.c_id where b.nid=a.b_id 测试代码提示出错.还有什么变通的方法 不 Can you ___us___helping others?A.join;/ B.join;in C.join;with D.join;on who would like A joining B to join C join left join问题比如 a left jooin b on a.id = b.id_ 这样 如果b中记录有两个一样id_的值与a中id 相同这样会查出来两条记录如何只查出来一条记录? 根据SQL:select a.a,a.b,a.c,b.c,b.d,b.f from a LEFT OUT JOIN b ON a.a = b.c写出右外连接 关于 FROM a,b 和 a LEFT JOIN b 的区别 ...简单的讲就是SELECT * FROM a,b WHERE a.id=b.id和 SELECT * FROM a LEFT JOIN b ON a.id=b.id这两种写法有什么区别么 ...糊涂了 ...求教 ... Thank you for ___this evening .A join us B join in us C joining us D joining in usjoin in us与 join us 的区别 inner join 与 left join 有何区别? ORACLE 中 select B.f from a A left join b B on A.e=B.e 如果B.f为空,B.f为0.怎么实现. We will play basketball.Wil you _ us?A.join in B.join C.join to D.join with i (would like to join) the basketball club.A.like to join B.want to join C.join Tom was a black slave and he at last ______ the cotton farm to join the North Army.A.left B.escaped C.ran away D.fled