oracle - 在查询中使用别名导致“命令未正确结束”

Question

我试过这个：

SELECT *
FROM (SELECT *
           , ROW_NUMBER() OVER (ORDER BY vernum DESC, defvern DESC) AS RowNumber
      FROM   MyTable
             INNER JOIN AnotherTable ON MyTable.id = AnotherTable.dataid
      WHERE  MyTable.defid = 123456 
             AND MyTable.attrid = 10) AS a
WHERE a.RowNumber = 1;

我收到此错误：

ORA-00933: SQL command not properly ended
00933. 00000 -  "SQL command not properly ended"
*Cause:    
*Action:
Error at Line: 8 Column: 37

当我删除AS a并且WHERE a.RowNumber = 1;查询工作正常时。

我不能将子查询分配给别名有什么原因吗？

Answer 1

Oracle 不支持使用as.

例如：

SQL> select 1
  2  from dual as a;
from dual as a
             *
ERROR at line 2:
ORA-00933: SQL command not properly ended


SQL> select 1
  2  from dual a;

         1
----------
         1

一样的方法：

SQL> select *
  2  from (
  3        select 1 from dual
  4       ) as a;
     ) as a
          *
ERROR at line 4:
ORA-00933: SQL command not properly ended


SQL> select *
  2  from (
  3        select 1 from dual
  4       )  a;

         1
----------
         1

列别名可以有也可以没有as：

SQL> select 1 as one, 2 two
  2  from dual;

       ONE        TWO
---------- ----------
         1          2