select a.* from a,b where a.num=b.num(+) 外连接,查询结果满足a.num=b.num以及a表有而b表没有的数据,等同于 select a.* from a,b where a.num=b.num union all select a.* from a where a.num not in (select num from b);
select a.* from a,b where a.num=b.num(+) 相当于下面的 select a.* from a left outer join b on a.uuid=b.uuid a、b左外连接以后把所有属于b的都不打印。不知道lz是不是想写这句 select * from a,b where a.num=b.num(+) select * from a left outer join b on a.uuid=b.uuid
外连接,查询结果满足a.num=b.num以及a表有而b表没有的数据,等同于
select a.* from a,b where a.num=b.num
union all
select a.* from a where a.num not in (select num from b);
相当于下面的
select a.* from a left outer join b on a.uuid=b.uuid
a、b左外连接以后把所有属于b的都不打印。不知道lz是不是想写这句
select * from a,b where a.num=b.num(+)
select * from a left outer join b on a.uuid=b.uuid