<>一、效率高的写法

1.无ORDER BY排序的写法。(效率最高)
(经过测试,此方法成本最低,只嵌套一层,速度最快!即使查询的数据量再大,也几乎不受影响,速度依然!)
SELECT * FROM (SELECT ROWNUM AS rowno, t.* FROM emp t WHERE hire_date BETWEEN
TO_DATE ('20060501', 'yyyymmdd') AND TO_DATE ('20060731', 'yyyymmdd') AND
ROWNUM <= 20) table_alias WHERE table_alias.rowno >= 10;
2.有ORDER BY排序的写法。(效率较高)
(经过测试,此方法随着查询范围的扩大,速度也会越来越慢哦!)
SELECT * FROM (SELECT tt.*, ROWNUM AS rowno FROM ( SELECT t.* FROM emp t WHERE
hire_date BETWEEN TO_DATE ('20060501', 'yyyymmdd') AND TO_DATE ('20060731',
'yyyymmdd') ORDER BY create_time DESC, emp_n

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