Question

我尝试在查询的WHERE子句中使用子查询的结果。我想要使用的属性是last_contact。见下文。

  SELECT forename, surname, type,
         ( SELECT MAX(completed_date)
             FROM tblTasks
            WHERE prospect_id = tblProspects.prospect_id AND completed = '1'
         ) AS last_contact,
         created_at 
    FROM tblProspects 
   WHERE hidden != '1' AND type='Prospect' AND last_contact > DATE_ADD(CURDATE(), INTERVAL -90 DAY) 
ORDER BY last_contact ASC

我收到SQL错误：＃1054 - 'where子句'中的未知列'last_contact'

非常感谢任何帮助。

感谢。

Answer 1

你需要使用HAVING子句来通过自定义别名coulmn来优化你的结果，它们不能在where子句中使用

SELECT 
forename, 
surname, 
type,
(SELECT MAX(completed_date) FROM tblTasks WHERE prospect_id = tblProspects.prospect_id AND completed = '1') AS last_contact, 
created_at 
FROM tblProspects 
WHERE hidden != '1' AND type='Prospect' 
HAVING (
last_contact > DATE_ADD(CURDATE(), INTERVAL -90 DAY)
OR last_contact IS NULL
)
ORDER BY last_contact ASC

在WHERE CLAUSE中使用子查询的结果

1 个答案: