Oracle 分页

详解Oracle的几种分页查询语句： http://database.51cto.com/art/200904/118737.htm
ORACLE大数据量下的分页解决方法: http://ddkangfu.blog.51cto.com/311989/1425797/
oracle 分页数据重复数据不正确: https://my.oschina.net/u/852445/blog/402325
实例：

SELECT * 
			FROM
			(
			SELECT RS.AMOUNT,RS.AREA,RS.AREANAME,[color=red]ROWNUM rn
			FROM
			(
			SELECT (
			CASE 
			WHEN oy.AMOUNT IS NULL THEN
			    ny.AMOUNT-0
			WHEN ny.AMOUNT IS NULL THEN
			    0-oy.AMOUNT
			ELSE
			   ny.AMOUNT-oy.AMOUNT
			END) AS amount,NY.AREA,NY.areaName
			FROM
			(SELECT "SUM"(VI.AMOUNT) AS AMOUNT ,VI.AREA, dm.AREA_NAME as areaName FROM VI_INCOME_ITEM_MAPPING VI 
			LEFT JOIN DM_AREA dm ON VI.AREA = dm.AREA_CODE
			WHERE VI.T_ITEM =  #{BudgetTItem,jdbcType=VARCHAR} AND VI.BLEVEL ='3'
			AND "SUBSTR"(VI.TXN_DATE,1,6) <![CDATA[ >= ]]>  #{startMonth,jdbcType=VARCHAR}
		    AND "SUBSTR"(VI.TXN_DATE,1,6)  <![CDATA[ <= ]]>  #{endMonth,jdbcType=VARCHAR}
			GROUP BY VI.AREA,dm.AREA_NAME) ny
			LEFT JOIN 
			(SELECT "SUM"(VI.AMOUNT) AS AMOUNT ,VI.AREA, dm.AREA_NAME as areaName FROM VI_INCOME_ITEM_MAPPING VI 
			LEFT JOIN DM_AREA dm ON VI.AREA = dm.AREA_CODE
			WHERE VI.T_ITEM = #{BudgetTItem,jdbcType=VARCHAR} AND VI.BLEVEL ='3'
			AND "SUBSTR"(VI.TXN_DATE,1,6) <![CDATA[ >= ]]> #{lastStartMonth,jdbcType=VARCHAR} 
			AND "SUBSTR"(VI.TXN_DATE,1,6)  <![CDATA[ <= ]]> #{lastEndMonth,jdbcType=VARCHAR} 
			GROUP BY VI.AREA,dm.AREA_NAME) oy
			ON NY.AREA = OY.AREA
			ORDER BY amount DESC ) [color=red]rs WHERE ROWNUM <= 10) WHERE rn >0

注意红色字体内层用ROWNUM，外层用RN，Oracle 一般第一次select时，有ROWNUM，可在第二层分页

分页两种方法：
第一种：

SELECT * FROM (SELECT t.*,ROWNUM as rowno FROM (SELECT * FROM test ORDER BY ADD_TIME ) t )
 WHERE rowno  BETWEEN 200001 AND 300000;

第二种：

SELECT * FROM ( SELECT t.*,ROWNUM as rowno FROM (SELECT * FROM test ORDER BY ADD_TIME) t WHERE ROWNUM  <= 300000)
WHERE rowno >=200001

第二种比第一种有效，因为第二种锁定了分页结果集，而第一种是从表所有记录中，分页；
对于两层嵌套的分页查询如：
实例：

select （select * from test ORDER BY ADD_TIME） where ROWNUM between 100000 and 200000

对于含排序（ORDER BY ADD_TIME），则排序字段ADD_TIME字段必须是唯一索引，否则已出现
结果集为空，或数据重复，含排序的正确做法如上面两种分页方式，再加一层嵌套。

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