PHP MySQL选择与WHERE列未找到？

Question

我试图用WHERE条件在MySQL PHPPDO从SELECT AS，我得到了错误

SQLSTATE[42S22]: Column not found: 1054 Unknown column 'total_consumers' in 'where clause'null 

我的查询：

SELECT category.* , SUM(Consumer.capacity) AS total_consumers 
FROM company AS company 
RIGHT JOIN company AS Consumer ON (Consumer.category_id = company.category_id AND Consumer.company_type = 'Consumer' ) 
RIGHT JOIN category AS category ON (category.category_id = company.category_id ) 
WHERE total_consumers > 0 
GROUP BY category.category_title 

目标：

我想所有记录Inc分类表，它们应该作为消费者和生产者存在于公司表中，如果消费者null不选择它

这里是上面的查询

的JSON结果如果我删除WHERE条件我得到了以下JSON响应

http://json.live/166EaR

就像你看到的一些记录有total_consumers : null不应该选择

任何想法如何做我的观点:(为什么我不能在WHERE语句中使用SELECT AS）

WHERE total_consumers > 
or 
WHERE total_consumers != null 
or 

WHERE xx NOT NULL 

Answer 1

您不能在where子句中使用来自select的别名。您必须使用having子句：

SELECT category.* , SUM(Consumer.capacity) AS total_consumers 
FROM company AS company 
RIGHT JOIN company AS Consumer ON (Consumer.category_id = company.category_id AND Consumer.company_type = 'Consumer' ) 
RIGHT JOIN category AS category ON (category.category_id = company.category_id ) 
GROUP BY category.category_title 
having total_consumers > 0