Question

在Oracle中，下面的Sql Server查询等同于什么：

select dd.dname, e.ename
from emp e
outer apply 
(select top 1 dname from dept d where d.did=e.did order by bdate) dd

请注意，实际查询非常不同，但概念是相同的。请原谅我上面的查询中的任何语法错误。

我在Oracle查询下面尝试过：

select dd.dname, e.ename
from emp e
left join 
(select * from 
(select dname from dept d where d.did=e.did order by bdate)
where rownum=1) dd

但是，它给出了以下错误：

Error at Command Line:6 Column:18
Error report:
SQL Error: ORA-00905: missing keyword
00905. 00000 -  "missing keyword"
*Cause:    
*Action:

Answer 1

加入后

On子句丢失了。因此，我将查询转换为逐个查询，它可以工作：

select dd.dname, e.ename
from emp e
left join 
(select min(bdate), dname, did from dept d group by dname, did)dd
on dd.did=e.did

Answer 2

您可以先排列行，然后排第一行：

select e.ename, d.dname
  from emp e
  left join  (
      select dept.dname, dept.did, row_number()
         over (partition by did order by bdate) rn from dept) d
    on e.did = d.did and d.rn=1

^SQLFiddle

迁移SQL Server将查询应用于Oracle

2 个答案: