如何在select语句中向子查询添加列别名？

Question

我正在尝试运行查询,我在select语句中使用子查询.
这有效:

select   
(select sysdate from dual),   
(select 'municipality' from dual),  
(select count(*) from municipality)  
from dual;  

但是生成的列名很难看,因此我想添加列别名.

我正在尝试运行以下查询:

select   
(select sysdate from dual) as sysdate,   
(select 'municipality' from dual) as tablename,  
(select count(*) from municipality) as count  
from dual;

这与ORA 00923失败:从找不到预期错误的关键字.不知怎的,我错过了一些东西.

有什么建议？

谢谢.

Answer 1

尝试用双引号括起来，

select
   (select sysdate from dual) as "sysdate",
   (select 'municipality' from dual) as "tablename",
   (select count(*) from municipality) as "count"
from dual;

SysDate是保留关键字。虽然，COUNT是一个聚合函数，但它是允许使用的。

• Oracle 保留关键字