具有（来自）别名的SQL子查询

我需要有关select子句中的子查询的帮助。我有表格：员工（员工ID、员工姓名、员工组）和活动（活动日期、活动状态、员工ID）。我需要为“W”集团的员工选择一些活动

不幸的是，我不能使用CREATETABLE/VIEW函数，所以我尝试了这个，但它不起作用

SELECT DISTINCT

TB1.EMPLOYEE_NAME,
(SELECT TB1.ACTIVITY_DATE FROM TB1 
WHERE TB1.ACTIVITY_STATUS = 'START' AND TB1.ACTIVITY_NUMBER = 1) AS FIRST_START,
(SELECT TB1.ACTIVITY_DATE FROM TB1 
WHERE TB1.ACTIVITY_STATUS = 'START' AND TB1.ACTIVITY_NUMBER = 2) AS SECOND_START,
(SELECT TB1.ACTIVITY_DATE FROM TB1 
WHERE TB1.ACTIVITY_STATUS = 'STOP' AND TB1.ACTIVITY_NUMBER = 1) AS FIRST_STOP,
(SELECT TB1.ACTIVITY_DATE FROM TB1 
WHERE TB1.ACTIVITY_STATUS = 'STOP' AND TB1.ACTIVITY_NUMBER = 2) AS SECOND_STOP

FROM( 

     SELECT DISTINCT

     A.EMPLOYEE_NAME,        
     B.ACTIVITY_DATE,
     B.ACTIVITY_STATUS,
     ROW_NUMBER() OVER (PARTITION BY A.EMPLOYEE_NAME,B.ACTIVITY_STATUS 
       ORDER BY B.ACTIVITY_DATE ASC) ACTIVITY_NUMBER

     FROM 
     (SELECT * FROM EMPLOYEES WHERE EMPLOYEE_GROUP ='W')  A

     LEFT JOIN ( SELECT * FROM ACTIVITIES  WHERE ACTIVITY_STATUS IN ('START','STOP','PAUSE') )B
      ON A.EMPLOYEE_ID = B.EMPLOYEE_ID

  ) TB1

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您知道我可以使用哪些函数从带有别名的表中选择数据吗？

我不确定您的Oracle版本是否支持它，但您必须将TB1定义为CTE（通用表表达式）：

---

或者，老式的方法是复制粘贴“TB1”每个实例的定义。（是的，真的，我们以前就是这样做的。）

您试过CTE（公共表表达式）吗？在Oracle文档中，公共表表达式称为子查询分解。至少这是我最后一次阅读Oracle文档。

WITH TB1 AS ( 

     SELECT DISTINCT

     A.EMPLOYEE_NAME,        
     B.ACTIVITY_DATE,
     B.ACTIVITY_STATUS,
     ROW_NUMBER() OVER (PARTITION BY A.EMPLOYEE_NAME,B.ACTIVITY_STATUS 
       ORDER BY B.ACTIVITY_DATE ASC) ACTIVITY_NUMBER

     FROM 
     (SELECT * FROM EMPLOYEES WHERE EMPLOYEE_GROUP ='W')  A

     LEFT JOIN ( SELECT * FROM ACTIVITIES  WHERE ACTIVITY_STATUS IN ('START','STOP','PAUSE') )B
      ON A.EMPLOYEE_ID = B.EMPLOYEE_ID

  )
SELECT DISTINCT

TB1.EMPLOYEE_NAME,
(SELECT TB1.ACTIVITY_DATE FROM TB1 
WHERE TB1.ACTIVITY_STATUS = 'START' AND TB1.ACTIVITY_NUMBER = 1) AS FIRST_START,
(SELECT TB1.ACTIVITY_DATE FROM TB1 
WHERE TB1.ACTIVITY_STATUS = 'START' AND TB1.ACTIVITY_NUMBER = 2) AS SECOND_START,
(SELECT TB1.ACTIVITY_DATE FROM TB1 
WHERE TB1.ACTIVITY_STATUS = 'STOP' AND TB1.ACTIVITY_NUMBER = 1) AS FIRST_STOP,
(SELECT TB1.ACTIVITY_DATE FROM TB1 
WHERE TB1.ACTIVITY_STATUS = 'STOP' AND TB1.ACTIVITY_NUMBER = 2) AS SECOND_STOP

FROM TB1