Question

我正在加入一些表，使用COUNT()为总计选择一列。此查询适用于返回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`

但是现在我正在尝试创建一个查询WHERE子句中的total的查询，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

返回错误total是未知列。有什么想法吗？

Answer 1

列别名不能在WHERE子句中使用。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

您还可以重复＆＃34; total＆＃34;的整个定义。在WHERE中 - 智能优化器很可能会生成相同的计划，但出于可读性考虑，我不会这样做。

在WHERE子句中使用子查询结果列时的未知列

1 个答案: