SQLServer2012子查询练习

表结构与数据：https://github.com/XuePeng87/TSQLV4

练习1

练习内容：编写一个查询，返回Orders表中能够查到的活动最后一天的全部订单

涉及的表：Sales.Orders

输出的列：orderid, orderdate, custid, empid

正确结果：4行

SELECT orderid, orderdate, custid, empid 
FROM Sales.Orders 
WHERE orderdate = (
	SELECT MAX(orderdate) FROM Sales.Orders
);

练习2

练习内容：编写一个查询，返回订单数量最多的客户的全部订单。注意，在一个以上的客户可能具备相同数量的订单

涉及的表：Sales.Orders

输出的列：custid, orderid, orderdate, empid

正确结果：31行

SELECT custid, orderid, orderdate, empid 
FROM Sales.Orders 
WHERE custid = 
(
	SELECT TOP 1 WITH TIES custid FROM Sales.Orders GROUP BY custid ORDER BY COUNT(*) DESC
);

练习3

练习内容：编写一个查询，返回在2016年5月1日或以后没有下订单的雇员

涉及的表：HR.Employees, Sales.Orders

输出的列：empid, firstname, lastname

正确结果：4行

SELECT empid, firstname, lastname 
FROM HR.Employees E 
WHERE E.empid NOT IN (
	SELECT O.empid FROM Sales.Orders AS O 
	WHERE O.orderdate >= '20160501'
);

练习4

练习内容：编写一个查询，返回有客户可是没有雇员的国家

涉及的表：Sales.Customers, HR.Employees

输出的列：country

正确结果：19行

SELECT DISTINCT country FROM Sales.Customers
WHERE country NOT IN (
	SELECT country FROM HR.Employees
);

练习5

练习内容：编写一个查询，返回每一个客户活动最后一天的全部订单

涉及的表：Sales.Orders

输出的列：custid, orderid, orderdate, empid

正确结果：90行

SELECT O1.custid, O1.orderid, O1.orderdate, O1.empid 
FROM Sales.Orders AS O1 WHERE O1.orderdate = (
	SELECT MAX(O2.orderdate) FROM Sales.Orders AS O2 
	WHERE O2.custid = O1.custid
);

练习6

练习内容：编写一个查询，返回2015年下过订单，可是2016年没有下订单的客户

涉及的表：Sales.Customers, Sales.Orders

输出的列：custid, companyname

正确结果：7行

SELECT custid, companyname FROM Sales.Customers AS C 
WHERE EXISTS (
	SELECT * FROM Sales.Orders AS O1 
	WHERE orderdate BETWEEN '20150101' AND '20151231' AND O1.custid = C.custid 
) AND NOT EXISTS (
	SELECT * FROM Sales.Orders AS O2 
	WHERE orderdate BETWEEN '20160101' AND '20161231' AND O2.custid = C.custid 
);

练习7

练习内容：编写一个查询，返回订购了产品12的客户

涉及的表：Sales.Customers, Sales.Orders, Sale.OrderDetails

输出的列：custid, companyname

正确结果：12行

SELECT custid, companyname 
FROM Sales.Customers WHERE custid IN (
	SELECT custid FROM Sales.Orders WHERE orderid IN (
		SELECT orderid 
		FROM Sales.OrderDetails 
		WHERE productid = 12
	)
);

练习8

练习内容：编写一个查询，计算每一个客户及其月度的采购总量

涉及的表：Sales.CustOrders

输出的列：custid, ordermonth, qty

正确结果：636行

SELECT custid, ordermonth, qty, (
	SELECT SUM(qty) FROM Sales.CustOrders AS O2 
	WHERE O2.custid = O1.custid
	AND O2.ordermonth <= O1.ordermonth
)  AS runqty 
FROM Sales.CustOrders AS O1;