Question

我有下表名为Messages：

ID | CustomerID | CarID | TruckID | CreatedByID | Date
1         23        null     null        2343    1/27/2014
2         null        56     null        2343    1/27/2014
3         null      null       78        2343    1/27/2014

消息可以与客户，汽车或卡车相关联。 Car Car和Truck也将拥有CustomerID，因此虽然特定消息可能是Car，但它也与客户相关联。

a）在上面的示例中，如果Car 56和Truck 78都属于Customer 23，则客户2343帮助的总数为1.

b）如果Car 56和Truck 78属于不同的客户，则总数为3。

我现在确定如何查询这个，我有这个查询，但它应该只给我汽车的总数（大多数消息将用于汽车）。

(SELECT CreatedByID, count(distinct(CarID)) AS Count 
 FROM Messages 
 WHERE CarID is not null 
   AND CreatedDate >= @StartDate 
   AND CreatedDate <= @EndDate 
   AND CreatedByID IN 
       (SELECT UserID FROM @UserIDs) 
 GROUP BY CreatedByID
) TotalCustomers on TotalCustomers .CreatedByID = u.UserID

所以在示例b中我应该只得到1，但那不正确。

如何修改此项以考虑示例b？

@UsersIDs是一个只有UserIDs的临时表

我尝试了这个，但我不认为这是正确的（并没有考虑卡车，我不确定它可以）。此外，我对CreatedByID进行了硬编码，当我尝试将查询更改为具有与上述类似的分组时，我无法正确执行此操作。

select CarID 
from Card 
where CustomerID not in (
    select CustomerID 
    from Messages 
    where CustomerID is not null 
      and CreatedByID  = 2343 
      and CreateDate >= @StartDate 
      AND CreateDate <= @EndDate 
    )
  and CarID in (
    select CarID 
    from Messages 
    where CarID is not null 
      and CreatedByID  = 2343 
      and CreateDate >= @StartDate 
      AND CreateDate <= @EndDate
    )

Answer 1

您的数据每封邮件只定义一个实体。假设是这种情况，你可以这样做：

select coalesce(m.customerid, c.customerid, t.customerid) as customerid, count(*) as cnt
from Messages m left outer join
     Cars c
     on m.carid = c.carid left outer join
     Trucks t
     on m.truckid = t.truckid
group by coalesce(m.customerid, c.customerid, t.customerid);

您可以为示例代码建议的其他过滤添加where子句。

注意：count(*)假定至少有一个ID与其他表中的一个匹配。

Answer 2

如果您想要帮助的客户数量，按createdByID小计，那么它将是这样的：

SELECT  m.createdByID
    --, m.CreatedDate --if you wanted the count of customers helped by date, then un-comment this line
    , COUNT(DISTINCT COALESCE(m.CustomerID, c.CustomerID, t.CustomerID)) as CustomersHelpedCount
FROM [Messages] m 
    LEFT JOIN Cars c ON m.carID = c.carID
    LEFT JOIN Trucks t on t.truckID = m.truckID
WHERE m.CreatedDate between @StartDate and @EndDate
    AND m.createdByID in (SELECT UserID FROM @UserIDs)
GROUP BY m.createdBy
    --, m.CreatedDate --if you wanted the count of customers helped by date, then un-comment this line

如何在可以与不同表关联时获取不同数量的ID？

2 个答案: