Question

我有一个包含以下列的客户表

 CustomerID, CustomerName, ParentCustomerID

如何从此表中获得拥有最多子女数量的客户？

Answer 1

这样的事情应该有效，但我怀疑这是最有效的方法。

此外，我自己也没有这样做，所以可能需要一点点按摩才能让它发挥作用。：）

select customerId, CustomerName
from
    customers
where customerId = (
    select top 1 ParentCustomerID 
    from
        customers
    group by ParentCustomerID
    order by count(*) desc
)

Answer 2

我想你会想要这个。

select top 1
    PARENT.CustomerID,
    NumberOfChildren = count(CHILD.CustomerID)
from customers PARENT
left join customers CHILD on PARENT.CustomerID = CHILD.ParentCustomerID
group by PARENT.CustomerID 
order by NumberOfChildren desc

这样就可以通过将表连接到自身来避免子查询的需要，并且非常有效。

Answer 3

您可以尝试这样的事情：

;WITH CTE( ChildCount, ParentCustomerID)
AS
(
  SELECT 
          COUNT(customerID) ChildCount,
          ParentCustomerID 
  FROM TABLE 
  GROUP BY ParentCustomerID
)
SELECT TABLE.CustomerId, TABLE.CustomerName
FROM CTE 
INNER JOIN TABLE 
ON 
TABLE.CustomerId = CTE.ParentCustomerID
AND 
CTE.ChildCount = (SELECT MAX(ChildCount) FROM CTE);

Answer 4

尝试使用此Stamtent来解决问题

SELECT TOP 1 ParentCustomerID, COUNT(customerID)
FROM customer 
GROUP BY ParentCustomerID

sql父子关系查询

4 个答案: