PHP MySQL選擇與WHERE列未找到？

Question

我試圖用WHERE條件在MySQL PHPPDO從SELECT AS，我得到了錯誤

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

我的查詢：

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 

目標：

我想所有記錄Inc分類表，它們應該作爲消費者和生產者存在於公司表中，如果消費者null不選擇它

這裏是上面的查詢

的JSON結果如果我刪除WHERE條件我得到了以下JSON響應

http://json.live/166EaR

就像你看到的一些記錄有total_consumers : null不應該選擇

任何想法如何做我的觀點:(爲什麼我不能在WHERE語句中使用SELECT AS）

WHERE total_consumers > 
or 
WHERE total_consumers != null 
or 

WHERE xx NOT NULL 

Answer 1

您不能在where子句中使用來自select的別名。您必須使用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