SQL

Question

我需要使用 SQL（确切地说是 SQL 服务器）从 Northwind 数据库中的 Orders table 获取以下数据：

查找在以下时间内至少下了 3 个订单的所有客户 (CustomerID) 间隔6个月(OrderDate).

因此，对于以下数据，查询应该 return 1

==========================
| CustomerID | OrderDate |
==========================
|      1     | 2000-1-1  |
--------------------------
|      1     | 2000-1-5  |
--------------------------
|      1     | 2000-4-30 |
--------------------------
|      2     | 2000-1-1  |
--------------------------
|      2     | 2000-5-30 |
--------------------------

Answer 1

SELECT N1.CustomerID, COUNT(N2.OrderDate)  FROM Northwind N1
INNER JOIN Northwind N2
ON N1.CustomerID=N2.CustomerID
AND N1.OrderDate<=Dateadd(MONTH, 6, N2.OrderDate)
GROUP BY N1.CustomerID
HAVING COUNT(N2.OrderDate)>=3

Answer 2

尝试以下操作：

SELECT OrderDate, CustomerID FROM orders GROUP BY OrderDate HAVING   COUNT(CustomerID) >= 3 ORDER BY COUNT(CustomerID) DESC

SQL - 查询未定义区间内的记录

SQL - Query records within an undefined interval

sql-server

datediff

northwind