MySQL - 按日期排序的查询无法获取最新记录

Question

我的数据库设置如下:

http://sqlfiddle.com/#!9/2c5fc

我想要做的是获取每个商店的列表及其最后的预算金额(每个计划的预算总额 * 他们对该计划的分配/100)。

某些商店可能没有为上次预算设置分配，因此我需要他们设置分配的最后预算，如果未设置分配或不存在预算，则为 NULL。

我有以下 SQL 查询:

SELECT s.StoreID,s.CentreID, budgetcalc.amount, budgetcalc.BudgetDate FROM store as s
LEFT JOIN centre on s.CentreID = centre.CentreID
LEFT JOIN (SELECT BudgetDate, SUM(sch.Amount*appt.Percentage/100) as amount, appt.StoreID from budget b
    INNER JOIN schedule as sch on b.BudgetID = sch.BudgetID
    INNER JOIN apportionment as appt on sch.ScheduleID = appt.ScheduleID 
    GROUP BY appt.StoreID, b.BudgetID
    ORDER BY STR_TO_DATE(b.BudgetDate,'%d-%m-%y') DESC
) as budgetcalc on s.StoreID = budgetcalc.StoreID
GROUP BY s.StoreID
ORDER BY s.StoreID, STR_TO_DATE(budgetcalc.BudgetDate,'%d-%m-%y') DESC;

但是，这存在不返回去年的问题，无论我返回子查询的顺序如何，它都会看似随机地返回前一年。

Answer 1

仅从表声明中计算出来是很困难的，但您需要获取每个商店的最新预算日期，然后将其与获取每个商店/预算的预算详细信息的子查询结合起来。

未经测试，但类似这样:-

SELECT s.StoreID,
        s.CentreID, 
        budgetcalc.amount, 
        budgetcalc.BudgetDate 
FROM store as s
LEFT OUTER JOIN centre ON s.CentreID = centre.CentreID
LEFT OUTER JOIN
(
    SELECT appt.StoreID, 
            MAX(BudgetDate) AS latestBudgetDate
    FROM budget b
    INNER JOIN schedule as sch ON b.BudgetID = sch.BudgetID
    INNER JOIN apportionment as appt ON sch.ScheduleID = appt.ScheduleID 
    GROUP BY appt.StoreID
) latest_budget
ON s.StoreID = latest_budget.StoreID 
LEFT OUTER JOIN 
(
    SELECT BudgetDate, 
            appt.StoreID, 
            SUM(sch.Amount*appt.Percentage/100) as amount 
    FROM budget b
    INNER JOIN schedule as sch ON b.BudgetID = sch.BudgetID
    INNER JOIN apportionment as appt ON sch.ScheduleID = appt.ScheduleID 
    GROUP BY appt.StoreID, b.BudgetID
) as budgetcalc 
ON latest_budget.StoreID = budgetcalc.StoreID
AND latest_budget.latestBudgetDate = budgetcalc.BudgetDate
ORDER BY s.StoreID, 
        budgetcalc.BudgetDate DESC;