获取无效标识符的错误

Question

SELECT emp. email_01 as online_id,
            emp. email_02 as primary_id,
            dept. email_03 as secondary_id
from 
(select distinct
           emp. email_01 as online_id,
            emp. email_02 as primary_id,
            dept. email_03 as secondary_id
    from emp, dept
    where emp.id=dept.id)

Answer 1

在这种情况下，您不需要有子查询：

SELECT DISTINCT
       emp.email_01  AS online_id,
       emp.email_02  AS primary_id,
       dept.email_03 AS secondary_id
FROM   emp
       INNER JOIN dept
       ON ( emp.id=dept.id )

您还可以使用ANSI连接语法而不是（令人困惑的）旧版Oracle逗号连接语法。