使用MySQL DAYNAME作为列标题，即使使用NULL结果

Question

我有一个查询可以处理大部分我需要的内容，但不能为空结果提供表示逻辑。

考虑这个查询：

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')) 

如果我得到的结果为每天星期我可以用PHP后期处理，并出示结果作为这样的：

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

然而，如果在任何一天没有订单，我显然得不到任何结果，并且我不能在后续流程中以一个列中的$ 0的价格出现。

我想也许是一个工作日表可能是一个JOIN的答案，但我无法想象它。像这样？

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

你这里语法wroing：

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

的AS条款需要在COALESCE功能外去。

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