Question

此查询会返回季度销售额，但我希望隐藏order_date列以显示在结果中。 order_date仅用于确定该季度是否购买了该商品。

SELECT item.item_id, item.item_name, item.item_type, item.item_price, SUM(orderdetail.order_quantity) AS 'Quantity Ordered', 
SUM(item.item_price*orderdetail.order_quantity) AS 'Total Sales Per Item', orders.order_date FROM item 
JOIN orderdetail ON item.item_id = orderdetail.item_id 
JOIN orders ON orderdetail.order_id = orders.order_id
GROUP BY item.item_id, item.item_name, item.item_price, item.item_type
HAVING order_date BETWEEN '2017-01-01' AND '2017-03-31'
ORDER BY item.item_id;

Answer 1

只需将其从select列表中删除即可。这不会阻止您在where或having条款中使用它：

SELECT item.item_id, item.item_name, item.item_type, item.item_price, SUM(orderdetail.order_quantity) AS 'Quantity Ordered', 
SUM(item.item_price*orderdetail.order_quantity) AS 'Total Sales Per Item'
-- order_date removed here
FROM item 
JOIN orderdetail ON item.item_id = orderdetail.item_id 
JOIN orders ON orderdetail.order_id = orders.order_id
GROUP BY item.item_id, item.item_name, item.item_price, item.item_type
HAVING order_date BETWEEN '2017-01-01' AND '2017-03-31'
ORDER BY item.item_id;

Answer 2

不要在select下包含它就像那样简单：）

SELECT item.item_id, item.item_name, item.item_type, item.item_price, SUM(orderdetail.order_quantity) AS 'Quantity Ordered', 
    SUM(item.item_price*orderdetail.order_quantity) AS 'Total Sales Per Item'  FROM item 
    JOIN orderdetail ON item.item_id = orderdetail.item_id 
    JOIN orders ON orderdetail.order_id = orders.order_id
    GROUP BY item.item_id, item.item_name, item.item_price, item.item_type
    HAVING order_date BETWEEN '2017-01-01' AND '2017-03-31'
    ORDER BY item.item_id

Answer 3

从SELECT中删除列，并将条件放在WHERE子句而不是HAVING子句中：

SELECT i.item_id, i.item_name, i.item_type, i.item_price, 
       SUM(od.order_quantity) AS `Quantity Ordered`, 
       SUM(i.item_price * od.order_quantity) AS `Total Sales Per Item`
FROM item i JOIN
     orderdetail od
     ON i.item_id = od.item_id JOIN
     orders o
     ON od.order_id = o.order_id
WHERE o.order_date BETWEEN '2017-01-01' AND '2017-03-31'
GROUP BY i.item_id, i.item_name, i.item_price, i.item_type
ORDER BY i.item_id;

注意：

查询使用表别名，使查询更容易编写和阅读。
条件应该放在WHERE子句中。它更有效，因为数据在聚合之前而不是之后过滤。

我不确定o.order_date是否应该在group by。如果你想为每个日期分别设一行，它应该只去那里。

如何排除列中出现的结果？

3 个答案: