SQL 连接限制

Question

我在获取下一个查询的第一行时遇到问题：

Select mar.Title MarketTitle, ololo.NUMBER, ololo.Title from Markets mar
JOIN( 
    Select emp.Employee_ID, emp.Market_id, ppp.Title, ppp.NUMBER from Employees emp
    JOIN(
    select pur.Employee_id Empl,Pro.Title Title, COUNT(pur.Product_id) NUMBER from Purchase pur
    LEFT JOIN  
        Payments pay ON pay.Payment_ID = pur.Payment_ID AND pay.Date > DATEADD(month, -1, GETDATE())
    RIGHT JOIN Products pro
    ON pur.Product_id = pro.Product_ID
    GROUP BY Pro.Title, pur.Employee_id) ppp ON ppp.Empl = emp.Employee_id) ololo
ON mar.Market_ID = ololo.Market_id
ORDER BY NUMBER DESC

我尝试了很多插入"limit 1"的组合，但都出错了。有人可以帮忙吗？

Answer 1

LIMIT 不适用于 SQL Server。

改用TOP 1：

SELECT TOP 1 mar.Title MarketTitle, ololo.NUMBER, ololo.Title from Markets mar
JOIN( 
    Select emp.Employee_ID, emp.Market_id, ppp.Title, ppp.NUMBER from Employees emp
    JOIN(
    select pur.Employee_id Empl,Pro.Title Title, COUNT(pur.Product_id) NUMBER from Purchase pur
    LEFT JOIN  
        Payments pay ON pay.Payment_ID = pur.Payment_ID AND pay.Date > DATEADD(month, -1, GETDATE())
    RIGHT JOIN Products pro
    ON pur.Product_id = pro.Product_ID
    GROUP BY Pro.Title, pur.Employee_id) ppp ON ppp.Empl = emp.Employee_id) ololo
ON mar.Market_ID = ololo.Market_id
ORDER BY NUMBER DESC

或OFFSET-FETCH与SQL Server 2012+:

SELECT  mar.Title MarketTitle, ololo.NUMBER, ololo.Title from Markets mar
JOIN( 
    Select emp.Employee_ID, emp.Market_id, ppp.Title, ppp.NUMBER from Employees emp
    JOIN(
    select pur.Employee_id Empl,Pro.Title Title, COUNT(pur.Product_id) NUMBER from Purchase pur
    LEFT JOIN  
        Payments pay ON pay.Payment_ID = pur.Payment_ID AND pay.Date > DATEADD(month, -1, GETDATE())
    RIGHT JOIN Products pro
    ON pur.Product_id = pro.Product_ID
    GROUP BY Pro.Title, pur.Employee_id) ppp ON ppp.Empl = emp.Employee_id) ololo
ON mar.Market_ID = ololo.Market_id
ORDER BY NUMBER DESC
OFFSET 0 ROWS
FETCH FIRST 1 ROW ONLY

Answer 2

从您的 SQL 中不清楚您要检索的内容。实际上，您会发现单个员工在所有时间内售出的单一产品的数量最多。然后你要返回他的市场和那个产品的名称。您的 pay.Date > dateadd(...) 没有影响，因为它处于 LEFT JOIN 中。由于您没有返回任何员工信息，我认为这不是您想要的...

如果您想要给定市场中数量最多的产品（？），SQL 将是：

    select top 1 mar.Title Market, 
    pro.Title Product,
    count(1) NUMBER
    from Markets mar
    join Employees emp
    on mar.Market_Id = emp.Market_id
    join Purchase pur
    on emp.Employee_id = pur.Employee_id 
    join Products pro
    on pur.Product_id = pro.Product_ID
    where pur.Date > DATEADD(month, -1, GETDATE())
    group by mar.Title, pro.Title
    order by count(1) desc

SQL 连接限制

SQL limit with joins

sql

sql-server

select

join

limit