Question

我在使MySql查询生效时遇到问题。基本上我们有表： “item”（带产品） “flags”（我们使用这些来标记旗帜特定产品） “itemflagassign”（表示哪些项目有哪些标志） “客户”和“ “customerorderpos”（订购商品）。

现在我创建了这个查询，它完美地显示了每个标志的总销售额：

SELECT t4.flagid, 
t4.name, 
COUNT(*) AS count_totalorders, 
SUM(t1.quantity_ordered - t1.quantity_cancelled) AS quantity_ordered, 
SUM(t1.itemtotal) AS item_total, 
SUM(t1.itemtotal - (quantity_ordered * t1.purchase_price)) AS item_earningstotal, 
((SUM(t1.itemtotal) / SUM(quantity_ordered * t1.purchase_price)) * 100) AS    item_calculationtotal 
FROM customerorderpos t1, customerorder t2, itemflagassign t3, flag t4
WHERE t2.customerorderid=t1.customerorderid and t2.datetime >= 1388534400 and t2.status_cancelled = 0 and t3.itemid=t1.itemid and     t4.flagid=t3.flagid
GROUP BY t4.flagid

但我想要包含没有销售的标志。这意味着它们存在于flag和itemflagassign表中，但在customerorder或customerorderpos中没有相应的记录。因此，我需要在指定日期范围内的客户订单或根本没有客户订单记录的记录。我已经尝试了一整天用左连接重写，但查询最终会永远运行（这些是大表，订单有100000多条记录）。

有什么想法吗？谢谢你的帮助！

Answer 1

select YourColumns ...
from itemflagassign t3
inner join flag t4 on t4.flagid = t3.flagid
left join customerorderpos t1 on t3.itemid = t1.itemid
left join customerorder t2 on t2.customerorderid = t1.customerorderid
    and t2.datetime >= 1388534400
    and t2.status_cancelled = 0
group by ...

Answer 2

解决了！我尝试过的每个连接都让查询永远运行...虽然在LEFT JOIN中放置了一个嵌套的SELECT，但是完美无缺：

SELECT t2.flagid, 
t2.name, 
COUNT(distinct t3.customerorderid) AS count_totalorders,
SUM(t3.quantity_ordered - t3.quantity_cancelled) AS quantity_ordered, 
SUM(t3.itemtotal) AS item_total, 
SUM(t3.itemtotal - (quantity_ordered * t3.purchase_price)) AS item_earningstotal,  
((SUM(t3.itemtotal) / SUM(quantity_ordered * t3.purchase_price)) * 100) AS item_calculationtotal 
FROM itemflagassign t1
JOIN flag t2 on t2.flagid=t1.flagid
LEFT JOIN (select tt2.customerorderid, itemid, quantity_ordered, quantity_cancelled, itemtotal, purchase_price from customerorderpos tt1, customerorder tt2 where tt1.customerorderid=tt2.customerorderid and tt2.datetime >= MY_DATE_FROM and tt2.datetime <= MY_DATE_TO and tt2.status_cancelled = 0) t3 on t3.itemid=t1.itemid
GROUP BY t2.flagid

来自4个表的mysql查询包含空记录（已解决：左连接内的嵌套选择）

2 个答案: