使用MySQL DAYNAME作爲列標題，即使使用NULL結果

Question

我有一個查詢可以處理大部分我需要的內容，但不能爲空結果提供表示邏輯。

考慮這個查詢：

SELECT 
SUM(order_detail.price/order_detail.qty*order_detail.qty_dispatched) AS orderedPrice, 
orders.location, 
orders.id, 
suppliers.supplier_name, 
DAYNAME(FROM_UNIXTIME(orders.datetime)) AS Day_Name, 
from_unixtime(orders.datetime) AS Day_Date 
FROM orders, order_detail, products,suppliers 
WHERE (orders.datetime BETWEEN '$from_date' AND '$to_date' 
AND order_detail.order_id = orders.id 
AND orders.location LIKE '%$locations%' 
AND order_detail.product_id=products.id 
AND products.supplier_id IN ($suppliers) 
AND suppliers.id IN ($suppliers) 
AND products.supplier_id=suppliers.id 
AND (orders.status <> 'deleted')) 

如果我得到的結果爲每天星期我可以用PHP後期處理，並出示結果作爲這樣的：

Location | Supplier Name | Mon | Tue | Wed | Thu | Fri | Sat | Sun | Total 
-------------------------------------------------------------------------- 
Alhambra | Widget Co  | $50 | $50 | $50 | $50 | $50 | $50 | $50 | $350 

然而，如果在任何一天沒有訂單，我顯然得不到任何結果，並且我不能在後續流程中以一個列中的$ 0的價格出現。

我想也許是一個工作日表可能是一個JOIN的答案，但我無法想象它。像這樣？

CREATE TABLE week_days(
    week_day_num INT(11) DEFAULT NULL 
); 

INSERT INTO week_days(week_day_num) VALUES (1),(2),(3),(4),(5),(6),(7); 

SELECT 
DAYNAME(FROM_UNIXTIME(orders.datetime)) AS day_name, 
SUM(order_detail.price/order_detail.qty*order_detail.qty_dispatched) AS orderedPrice, 
COALESCE(SUM(order_detail.price/order_detail.qty*order_detail.qty_dispatched) AS orderedPrice , 0) 
FROM week_days wd 
LEFT JOIN (

SELECT 
orders.location, 
orders.id, 
suppliers.supplier_name, 
from_unixtime(orders.datetime) AS Day_Date 
FROM orders, order_detail, products,suppliers 
WHERE (orders.datetime BETWEEN '$from_date' AND '$to_date' 
AND order_detail.order_id = orders.id 
AND orders.location LIKE '%$locations%' 
AND order_detail.product_id=products.id 
AND products.supplier_id IN ($suppliers) 
AND suppliers.id IN ($suppliers) 
AND products.supplier_id=suppliers.id 
AND (orders.status <> 'deleted')) 


) order_results 
ON wd.week_day_num = DAYOFWEEK(FROM_UNIXTIME(orders.datetime)) 
GROUP BY 
     products.supplier_id,orders.location,DAYOFWEEK(FROM_UNIXTIME(orders.datetime)) 

ORDER BY location, products.supplier_id,Day_Date ASC; 

Answer 1

你這裏語法wroing：

COALESCE(SUM(order_detail.price/order_detail.qty*order_detail.qty_dispatched) AS orderedPrice , 0) 

的AS條款需要在COALESCE功能外去。

COALESCE(SUM(order_detail.price/order_detail.qty*order_detail.qty_dispatched), 0) AS orderedPrice