Question

所以我一直在处理查询几年，有时我会问自己是否有更简单的方法，或者更复杂的方式使其发挥作用。所以今天我遇到了一个情况，我有一张桌子，让我们说用户，我想对那张桌子进行几次比较。

在这种情况下，从我拥有的每个用户那里获取统计数据：了解他所做的订单数量，或者他在指定时间段内在愿望清单中有多少产品;例如上周和本周。所以我想知道的是，最好的方法是使用left joins和ifs这样：

SELECT 
users.id,
SUM(IF(wishlist.date = LAST_WEEK, 1, 0)) LAST_WEEK_WISHLIST,
SUM(IF(wishlist.date = THIS_WEEK, 1, 0)) THIS_WEEK_WISHLIST,
SUM(IF(orders.date = LAST_WEEK, 1, 0)) LAST_WEEK_ORDERS,
SUM(IF(orders.date = THIS_WEEK, 1, 0)) THIS_WEEK_ORDERS
FROM
users
LEFT JOIN wishlist ON users.id = wishlist.user_id
LEFT JOIN orders ON users.id = orders.user_id
... 
GROUP BY users.id
ORDER BY users.id ASC

......或者是否有更好或更优化的方法来实现这一目标。

提前致谢

Answer 1

我建议尝试使用子查询而不是加入这可能会产生影响

这是我如何解决这个问题的一个例子

SELECT l_outer.Locations_LocationID, l_outer.Locations_LocationName,

ifnull((SELECT format(sum(replace(Payments_Amount, '$', '')), 2) as card_total
    FROM Payments as p
    where p.Payments_PaymentItem in ('Visa', 'MasterCard', 'Discover') AND p.Payments_LocationID = l_outer.Locations_LocationID AND STR_TO_DATE(Payments_Date, '%m/%d/%Y') >= DATE_SUB(curdate(),INTERVAL (DAY(curdate())-1) DAY)
    group by p.Payments_LocationID), 0.00) Cards,

ifnull((SELECT format(sum(replace(Payments_Amount, '$', '')), 2) as AmericanExpress_total
    FROM Payments as p
    where p.Payments_PaymentItem = 'American Express' AND p.Payments_LocationID = l_outer.Locations_LocationID AND STR_TO_DATE(Payments_Date, '%m/%d/%Y') >= DATE_SUB(curdate(),INTERVAL (DAY(curdate())-1) DAY)
    group by p.Payments_LocationID), 0.00) AmericanExpress

From Locations as l_outer

与MySQL中的表进行比较

1 个答案: