Come utilizzare l'Alias ​​nella clausola Where?

Question

Ho questa procedura:

 PROCEDURE P_LOAD_EXPIRED_ACCOUNT
  (
  pDayDiff IN NUMBER,
  ExpiredCur OUT MEGAGREEN_CUR
  )
  IS
  BEGIN
  OPEN ExpiredCur FOR
  SELECT 
  ACCOUNT_NAME, SERVICE_TYPE, 
      CASE 
      WHEN SERVICE_TYPE = 1 THEN ADD_MONTHS(ACTIVATED_DATE,3)
      WHEN SERVICE_TYPE = 2 THEN ADD_MONTHS(ACTIVATED_DATE,6)
      WHEN SERVICE_TYPE = 3 THEN ADD_MONTHS(ACTIVATED_DATE,12)        
       END 
       AS EXPIRED_DATE
  FROM SUBSCRIBERS
  WHERE (EXPIRED_DATE - CURRENT_DATE) < pDayDiff;
  END;

ma SQL Developer genera questo errore:

Errore(20,10):PL/SQL:ORA-00904:"DATA DI SCADENZA":identificatore non valido

Credo che PLSQL mi permetta di utilizzare la clausola Alias ​​in Where, ma c'è qualcosa che ho dimenticato?

Grazie in anticipo.

Answer 1

Non puoi fare riferimento all'alias di colonna nella clausola WHERE: le tue opzioni sono:

• replicare l'istruzione CASE nella clausola WHERE

• utilizzare una sottoquery:

  PROCEDURE P_LOAD_EXPIRED_ACCOUNT(pDayDiff NUMBER,
                                   ExpiredCur OUT MEGAGREEN_CUR)
  IS
  BEGIN
  
  
     OPEN ExpiredCur FOR
     SELECT x.account_name,
            x.service_type, 
            x.expired_date
       FROM (SELECT s.account_name,
                    s.service_type, 
                    CASE 
                       WHEN s.service_type = 1 THEN ADD_MONTHS(ACTIVATED_DATE,3)
                       WHEN s.service_type = 2 THEN ADD_MONTHS(ACTIVATED_DATE,6)
                       WHEN s.service_type = 3 THEN ADD_MONTHS(ACTIVATED_DATE,12)        
                    END AS EXPIRED_DATE
               FROM SUBSCRIBERS s) x
      WHERE x.expired_date - CURRENT_DATE < pDayDiff;
  
  
  END;
  

  Oracolo 9i+

  WITH summary AS (
    SELECT s.account_name,
           s.service_type, 
           CASE 
              WHEN s.service_type = 1 THEN ADD_MONTHS(ACTIVATED_DATE,3)
              WHEN s.service_type = 2 THEN ADD_MONTHS(ACTIVATED_DATE,6)
              WHEN s.service_type = 3 THEN ADD_MONTHS(ACTIVATED_DATE,12)        
           END AS EXPIRED_DATE
      FROM SUBSCRIBERS s)
     SELECT x.account_name,
            x.service_type, 
            x.expired_date
       FROM summary x
      WHERE x.expired_date - CURRENT_DATE < pDayDiff;