如何在Where子句中使用别名?
-
27-09-2019 - |
题
我有这个程序:
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;
但 SQL Developer 生成此错误:
错误(20,10):PL/SQL:ORA-00904:“EXPIRED_DATE”:不合法的识别符
我相信 PLSQL 允许我在 Where 子句中使用 Alias,但是我忘记了什么吗?
提前致谢。
解决方案
您不能在 WHERE 子句中引用列别名 - 您的选项是:
- 复制 WHERE 子句中的 CASE 语句
使用子查询:
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;
甲骨文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;
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