如何在 SQL 中加入带有 row_number() 函数的语句？

Question

我是一个带有 row_number() 函数的 SQL，我想加入其他表以获取以下字段。 我将如何做到这一点？

所需字段：

EMPLOYEE.EMPLID 
  EMPLOYEE.JOBTITLE
  NAME.FIRST_NAME
  NAME.LAST_NAME
  LOCATION.ADDRESS
  PROFESSIONAL_NAME.PROF_NAME 

开始 SQL：

SELECT COUNT(*) 
FROM 
    (
        SELECT EMPLOYEE.*, ROW_NUMBER() OVER (PARTITION BY EMPLID ORDER BY 
        PRIM_ROLE_IND DESC, EMPL_RCD ASC) as RN
        FROM EMPLOYEE
        WHERE JOB_INDICATOR = 'P'
    ) dt
WHERE RN = 1

当我尝试在末尾添加左连接时，我收到一条错误消息，显示“EMPLOYEE”。“EMLID”无效标识符。

我正在尝试什么：

SELECT 
  EMPLOYEE.EMPLID, 
  EMPLOYEE.JOBTITLE,
  NAME.FIRST_NAME, 
  NAME.LAST_NAME, 
  LOCATION.ADDRESS,
  PROFESSIONAL_NAME.PROF_NAME 
FROM 
    (
        SELECT EMPLOYEE.*, ROW_NUMBER() OVER (PARTITION BY EMPLID ORDER BY 
        PRIM_ROLE_IND DESC, EMPL_RCD ASC) as RN
        FROM EMPLOYEE
        WHERE JOB_INDICATOR = 'P'
    ) 
    
    LEFT JOIN NAME ON EMPLOYEE.EMPLID = NAME.EMPLID 
WHERE 
  RN = 1
  AND
  NAME.EFFDT = (
    SELECT 
      MAX (NAME2.EFFDT) 
    FROM 
      NAME NAME2 
    WHERE 
      NAME2.EMPLID = NAME.EMPLID 
      AND NAME.NAME_TYPE = 'PRI'
  )  
  AND EMPLOYEE.JOB_INDICATOR = 'P'

Answer 1

你只需要给你的表起别名

...
(
    SELECT EMPLOYEE.*, ROW_NUMBER() OVER (PARTITION BY EMPLID ORDER BY 
    PRIM_ROLE_IND DESC, EMPL_RCD ASC) as RN
    FROM EMPLOYEE
    WHERE JOB_INDICATOR = 'P'
) temp_employee --add this
LEFT JOIN NAME ON temp_employee.EMPLID = NAME.EMPLID 
...

当您在内部选择中使用 row_number() 创建新表时，您实际上是在创建一个新表。 您需要给该表起alias或命名，然后引用该别名。 在上面，您的from是内部选择，而不是 EMPLOYEE 表。 请参阅下面的简化示例。

select newtable.field from (select field from mytable) newtable