语法：ROW_NUMBER() OVER(PARTITION BY COLUMN ORDER BY COLUMN)简单的说
ROW_NUMBER()从1开始，为每一条分组记录返回一个数字，这里的ROW_NUMBER() OVER (ORDER BY CYLH DESC) 是先把xlh列降序，再为降序以后的每条CYLH记录返回一个序号。
示例：
分析：ROW_NUMBER() OVER (PARTITION BY COL1 ORDER BY COL2) 表示根据COL1分组，在分组内部根据 COL2排序，而此函数计算的值就表示每组内部排序后的顺序编号（组内连续的唯一的)
也可这样使用：ROW_NUMBER() OVER (ORDER BY COL2)
例子：
建立测试表，并插入测试数据
CREATE TABLE TEST_ROW_NUMBER_01(
CMZH varchar(10) not null,
CYLH varchar(10) null,
MJE money null,
);
INSERT INTO TEST_ROW_NUMBER_01(CMZH,CYLH,MJE) VALUES (2106000011,20281997,10.50) INSERT INTO TEST_ROW_NUMBER_01(CMZH,CYLH,MJE) VALUES(2106000010,20281996,10.50) INSERT INTO TEST_ROW_NUMBER_01(CMZH,CYLH,MJE) VALUES(2106000008,20281995,0.00) INSERT INTO TEST_ROW_NUMBER_01(CMZH,CYLH,MJE) VALUES(2106000006,20281994,9.50) INSERT INTO TEST_ROW_NUMBER_01(CMZH,CYLH,MJE) VALUES(2106000004,20281993,5.50) INSERT INTO TEST_ROW_NUMBER_01(CMZH,CYLH,MJE) VALUES(2106000001,20281992,10.50) INSERT INTO TEST_ROW_NUMBER_01(CMZH,CYLH,MJE) VALUES(2106000002,20281992,10.50) INSERT INTO TEST_ROW_NUMBER_01(CMZH,CYLH,MJE) VALUES(2106000007,20217280,0.00) INSERT INTO TEST_ROW_NUMBER_01(CMZH,CYLH,MJE) VALUES(2106000009,20172458,5.50) INSERT INTO TEST_ROW_NUMBER_01(CMZH,CYLH,MJE) VALUES(2106000005,20121813,0.00)
执行脚本自动生成行号并按CYLH进行排序（滑动查看代码）
SELECT ROW_NUMBER()OVER(ORDER BY CYLH DESC) AS ROWNUM,* FROM TEST_ROW_NUMBER_01
结果如下：
注意：在使用over等开窗函数时，over里头的分组及排序的执行晚于“where，group by，order by”的执行。
