sql父子关系查询 [英] sql parent child relationship query

问题描述

我的客户表为

CustomerID帐号Number ParentCustomerID
--------- ------------- -----------------

从中我如何才能找到拥有最多孩子的客户?

I am having a customer table as

CustomerID AccountNumber ParentCustomerID
- -------- ------------- -----------------

from this how can i find the customer which has most number of children ?

推荐答案

您可以使用左外连接声明"

选择顶部1个C.CustomerId，IsNull(Count(P.*)，0)
来自客户C
左外加入YOUR_PARENT_TABLE P开(A.ParentCustomerID = P.ParentCustomerID)
按IsNull(Count(P.*)，0)desc
排序
如果要查看所有记录，请省略前1个

You can use Left Outer Join Statment

Select top 1 C.CustomerId,IsNull(Count(P.*),0)
From CUSTOMER C
Left Outer Join YOUR_PARENT_TABLE P On ( A.ParentCustomerID= P.ParentCustomerID)
Order By IsNull(Count(P.*),0)desc

omit top 1 if you want to see all record

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