Question

我需要select子句中的子查询帮助。我有桌子：员工（EMPLOYEE_ID，EMPLOYEE_NAME，EMPLOYEE_GROUP）和活动（ACTIVITY_DATE，ACTIVITY_STATUS，EMPLOYEE_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CREATE TABLE / VIEW函数，所以我试过这个，但是它没有用。

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

你知道任何函数，我可以用它来从带有别名的表中选择数据吗？

Answer 1

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

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

或者，老式的方式是复制粘贴＆＃34; TB1＆＃34;的每个实例的定义。（是的，真的，这就是我们以前的做法。）

带有（from）别名的SQL子查询

1 个答案: