SqlServer_临时表查询和内联子查询的使用；

功能：查询订单表中每个顾客第一次下订单的订单号和时间；
(1)、临时表使用
USE AdventureWorks2008
GO
SELECT soh.CustomerID, MIN(soh.OrderDate) AS OrderDate
	INTO #MinOrderDates
	FROM Sales.SalesOrderHeader soh
	GROUP BY soh.CustomerID;
SELECT soh.CustomerID, soh.SalesOrderID, soh.OrderDate
	FROM Sales.SalesOrderHeader soh
	JOIN #MinOrderDates t
	ON soh.CustomerID = t.CustomerID
	AND soh.OrderDate = t.OrderDate
	GROUP BY soh.CustomerID
DROP TABLE #MinOrderDates
(2)、内联子查询
SELECT soh1.CustomerID, soh1.SalesOrderID, soh1.OrderDate
	FROM Sales.SalesOrderHeader soh1
	WHERE soh1.OrderDate  = (SELECT Min(soh2.OrderDate)
				FROM Sales.SalesOrderHeader soh2
				WHERE soh2.CustomerID = soh1.customerID)
	ORDER BY CustomerID;