Question

我已在SELECT中声明了变量upload_source，但收到错误消息

“ where子句”中的未知列“ upload_source”

   SELECT b.name as name, filename, upload_date, IF(filename LIKE '%.png%', 1, 0) as type, IF(ex_link!='', 0, 1) as upload_source, title, a.id
    FROM (`all_media` a)
    LEFT JOIN `admins` b ON `b`.`id`=`user_id`
    WHERE `a`.`approved` =  0
    AND `upload_source` =  0
    ORDER BY `filename` DESC

我该如何解决？

Answer 1

您不能在where子句中使用别名的表达式/列。在Select子句中使用相同的表达式（在Where子句中定义）。

来自as per the docs：

可以在查询选择列表中使用别名为列提供一个   不同的名字。您可以在GROUP BY，ORDER BY或HAVING中使用别名   子句引用该列。

标准SQL不允许在WHERE子句中引用列别名。   施加此限制是因为当WHERE子句是   进行评估，则可能尚未确定列值。

请改为执行以下操作（我已将upload_source = 0简化为ex_link != ''）：

 SELECT b.name as name, 
        filename, 
        upload_date, 
        IF(filename LIKE '%.png%', 1, 0) as type, 
        IF(ex_link!='', 0, 1) as upload_source, 
        title, 
        a.id
 FROM `all_media` AS a 
 LEFT JOIN `admins` b ON `b`.`id`=`user_id`
 WHERE `a`.`approved` =  0
   AND ex_link != '' 
 ORDER BY `filename` DESC

Answer 2

在SQL中， WHERE 关键字不能与集合函数一起使用。尝试使用具有条款：

SELECT b.name as name, filename, upload_date, IF(filename LIKE '%.png%', 1, 0) as type, IF(ex_link!='', 0, 1) as upload_source,title, a.id FROM ( all_media a) LEFT JOIN管理员b ON b . id = user_id WHERE a .已批准= 0 HAVING upload_source = 0 ORDER BY文件名DESC

Codeigniter MySQL列where子句中的未知列

2 个答案: