例如:
TRIP_BASEINFO 出差申请表共有1665条数据,使用sql developer进行性能分析。
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select * from ( select rownum rn, t.* from ( select trip.* from TRIP_BASEINFO trip ) t where rownum <= 100 ) t1 where t1.rn >= 90;
共用时间:cost = 11315
走全表扫描
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select trip1.* from ( select rownum rn, t.to_id from ( select trip.to_id from TRIP_BASEINFO trip ) t where rownum <= 100 ) t1 inner join TRIP_BASEINFO trip1 on t1.n_id = trip1.n_id where t1.rn >= 90;
以上to_id为主键
共用时间:cost = 171
走主键索引
此种分页语句最佳。
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select * from TRIP_BASEINFO where to_id in ( select to_id from ( select rownum rownum_, to_id from ( select to_ID from TRIP_BASEINFO ) where rownum <= 100 ) where rownum_ >= 90 )
共用时间:cost = 172
使用了in
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