我可以在where子句中使用select域中的somename作爲somename嗎？

Question

我正試圖讓totalQuantity小於alterQuantity的產品。

$this->db 
->select("products.id as productid, products.code as code, products.name, products.unit, products.price, sum(warehouses_products.quantity) as totalQuantity, products.alert_quantity as alertQuantity") 
->from('products') 
->where('alertQuantity >=', 'totalQuantity') 
->join('warehouses_products', 'products.id=warehouses_products.product_id, 'left') 
->group_by("products.id"); 

我得到的錯誤，在未知列'alertQuantity「where子句」如果我alertQuantity在where子句我得到未知列「totalQuantity」 products.alert_quantity「where子句」這一個我不知道如何改變，因爲這是數量的總和。你能幫我解決這個問題嗎？

我的問題： 我有選擇alert_quantity爲alertQuantity和金額（數量）爲totalQuantity

我可以使用alterQuantity和totalQuantity where子句中？

表結構

產品

ID，代碼，名稱，單元價格，alert_quantity

warehouses_products

ID，PRODUCT_ID，warehouse_id，數量

---

找到 我不能使用totalQuantity有沒有其他的想法，我怎麼能比較products.alert_quantity與sum（warehouses.products.quantity）？

Answer 1

嘗試這種::

select 
products.id as productid, 
products.code as code, 
products.name, products.unit, 
products.price, 
sum(products.alert_quantity) as totalQuantity, 
products.alert_quantity as alertQuantity 
from products 

LEFT join warehouses_products on products.id=warehouses_products.product_id 
where products.alert_quantity>= totalQuantity 
group_by products.id 

Answer 2

嘗試使用選擇第二個參數，如 變化

$this->db 
->select("products.id as productid, products.code as code, 
products.name, products.unit, products.price, 
sum(warehouses_products.quantity) as totalQuantity, 
products.alert_quantity as alertQuantity") 

到

$this->db 
->select("products.id as productid, products.code as code, 
products.name, products.unit, products.price, 
sum(warehouses_products.quantity) as totalQuantity, 
products.alert_quantity as alertQuantity", FALSE) 

和關閉引號加入部分

編輯，嘗試重新排序您的語句，如：

$this->db 
->select("products.id as productid, products.code as code, products.name, products.unit, products.price, sum(warehouses_products.quantity) as totalQuantity, products.alert_quantity as alertQuantity", FALSE) 
->from('products') 
->join('warehouses_products', 'products.id=warehouses_products.product_id', 'left') 
->where('alertQuantity >=', 'totalQuantity') 
->group_by("products.id");