oracle数据库 有三张表 用户表user（userid,username,company,deptid）,日志表log

嵌入的左连接。也就是像这样：select U.*,count(l.userid) from (select t.userid,t.username ,d.deptname from user t left outer join dept d on t.deptid = d.deptid group by t.userid,t.username) U left outer join log l on U.userid=l.userid

select * from table1 t1,table2 t2 where t1.id=t2.id

这样就是联合查询啊

left join

right join

inner join

详细的看 *** 作手册啊

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