在 WHERE 子句中使用子查询结果列时的未知列

Question

我有几张表要加入以使用COUNT() 选择总计列。此查询非常适合返回 total 列：

SELECT *,`excel`.`drivers`.`AutoNumber` AS `current_driver`,
(SELECT COUNT(`issues`.`categories`.`points`) FROM `issues`.`points` INNER JOIN `excel`.`drivers` ON `issues`.`points`.`driver_id` = `excel`.`drivers`.`AutoNumber` INNER JOIN `issues`.`categories` ON `issues`.`categories`.`id` = `issues`.`points`.`category_id` WHERE `excel`.`drivers`.`AutoNumber`=`current_driver`) AS `total` 
FROM `issues`.`points` 
INNER JOIN `excel`.`drivers` ON `issues`.`points`.`driver_id` = `excel`.`drivers`.`AutoNumber` 
INNER JOIN `issues`.`categories` ON `issues`.`categories`.`id` = `issues`.`points`.`category_id`

但现在我正在尝试创建一个查询来比较 WHERE 子句中的total，如下所示：

SELECT *,`excel`.`drivers`.`AutoNumber` AS `current_driver`,
(SELECT COUNT(`issues`.`categories`.`points`) FROM `issues`.`points` INNER JOIN `excel`.`drivers` ON `issues`.`points`.`driver_id` = `excel`.`drivers`.`AutoNumber` INNER JOIN `issues`.`categories` ON `issues`.`categories`.`id` = `issues`.`points`.`category_id` WHERE `excel`.`drivers`.`AutoNumber`=`current_driver`) AS `total` 
FROM `issues`.`points` 
INNER JOIN `excel`.`drivers` ON `issues`.`points`.`driver_id` = `excel`.`drivers`.`AutoNumber` 
INNER JOIN `issues`.`categories` ON `issues`.`categories`.`id` = `issues`.`points`.`category_id` WHERE `total` = 3

这会返回一个错误，即total 是一个未知列。有什么想法吗？

Answer 1

不能在WHERE 子句中使用列别名。试试

select a.* 
FROM 
(
SELECT [column_list]
,`excel`.`drivers`.`AutoNumber` AS `current_driver`,
(SELECT COUNT(`issues`.`categories`.`points`) FROM `issues`.`points` INNER JOIN `excel`.`drivers` ON `issues`.`points`.`driver_id` = `excel`.`drivers`.`AutoNumber` INNER JOIN `issues`.`categories` ON `issues`.`categories`.`id` = `issues`.`points`.`category_id` WHERE `excel`.`drivers`.`AutoNumber`=`current_driver`) AS `total` 
FROM `issues`.`points` 
INNER JOIN `excel`.`drivers` ON `issues`.`points`.`driver_id` = `excel`.`drivers`.`AutoNumber` 
INNER JOIN `issues`.`categories` ON `issues`.`categories`.`id` = `issues`.`points`.`category_id`
)a 
WHERE a.`total` >3

您还可以在 WHERE 中重复“总计”的整个定义 - 智能优化器很可能会生成相同的计划，但为了便于阅读，我不会这样做。