DECLARE @TestData TABLE(
ID INT IDENTITY(1,1),
Department VARCHAR(20),
LastName VARCHAR(20),
Rate FLOAT
)
INSERT INTO @TestData(Department,LastName,Rate)
SELECT 'Document Control','Arifin',17.7885 UNION ALL
SELECT 'Document Control','Norred',16.8269 UNION ALL
SELECT 'Document Control','Kharatishvili',16.8269 UNION ALL
SELECT 'Information Services','Chai',10.25 UNION ALL
SELECT 'Information Services','Berge',10.25 UNION ALL
SELECT 'Information Services','Trenary',50.4808 UNION ALL
SELECT 'Information Services','Conroy',39.6635 UNION ALL
SELECT 'Information Services','Ajenstat',38.4615 UNION ALL
SELECT 'Information Services','Wilson',38.4615 UNION ALL
SELECT 'Information Services','Connelly',32.4519 UNION ALL
SELECT 'Information Services','Meyyappan',32.4519
SELECT * FROM @TestData
這里以Department分區，則整個數據集被分成了兩部分：Information Services和Document Control兩塊，這時FIRST_VALUE分別返回兩塊分區內的首條數據值，同樣的受ORDER BY關鍵字的影響，
與FIRST_VALUE函數同時出現的還有一個，SECOND_VALUE？NO，沒有這個函數啊，但是有一LAST_VALUE，怎么函數怎么使用，不打算再單獨起一篇文章了，LAST_VALUE嗯
