按 SQL Oracle 中的计算列过滤 [重复]

【问题标题】：Filter by a calculated colum in SQL Oracle [duplicate]按 SQL Oracle 中的计算列过滤 [重复]
【发布时间】：2022-06-10 18:14:24
【问题描述】：

我正在尝试选择天数差异超过 50 的列。

但是我不能这样做。在我的查询下方找到：

SELECT name_,
       client_p as Client,
       to_date(first_date)-to_date(last_day) as difference
FROM   table1.mydata
where  difference>50

对此有何见解？

谢谢。

【问题讨论】：

标签： sql oracle

【解决方案1】：

你不能那样引用它；要么使用这个

SELECT name_,
       client_p AS client,
       TO_DATE (first_date) - TO_DATE (LAST_DAY) AS difference
  FROM table1.mydata
 WHERE TO_DATE (first_date) - TO_DATE (LAST_DAY) > 50;

或 - 将您的查询作为 CTE（或子查询）：

WITH
   temp
   AS
      (SELECT name_,
              client_p AS client,
              TO_DATE (first_date) - TO_DATE (LAST_DAY) AS difference
         FROM table1.mydata)
SELECT *
  FROM temp
 WHERE difference > 50;

【讨论】：

【解决方案2】：

您不能立即使用别名进行过滤。进行子查询并使用别名从中选择或更改为：

SELECT name_,
       client_p as Client,
       to_date(first_date)-to_date(last_day) as difference
FROM   table1.mydata
where  to_date(first_date)-to_date(last_day) > 50

【讨论】：