sql - 作为列的表达式和“没有这样的列”错误

Question

我有一个简单的查询：

SELECT ((interest_step / 12) * 365 + (MOD(interest_step, 12) * 30)) AS "days"
FROM "negotiations"."addon" WHERE (days <= 72)

但是当我执行它时，我得到一个错误：列'days'不存在。

我该如何纠正？

Answer 1

试试这个：

SELECT * 
FROM
(
   SELECT
     ((interest_step / 12) * 365 + (MOD(interest_step, 12) * 30)) AS "days" 
   FROM "negotiations"."addon" 
) t
WHERE (days <= 72)

那是因为WHERE子句在子句之前执行SELECT，因此它不会看到别名days。您应该将其包含在子查询中。

Answer 2

您不能在生成它的同一选择语句中引用列别名，这为您提供了两种选择：

SELECT ((interest_step / 12) * 365 + (MOD(interest_step, 12) * 30)) AS "days"
FROM "negotiations"."addon" 
WHERE (((interest_step / 12) * 365 + (MOD(interest_step, 12) * 30)) <= 72)

或者

SELECT *
FROM
(
  SELECT ((interest_step / 12) * 365 + (MOD(interest_step, 12) * 30)) AS "days"
  FROM "negotiations"."addon" 
) A
WHERE (days <= 72)