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2011-05-01 17:25:19| 分类： ABAP基础知识 | 标签： |举报 |字号大中小订阅

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0.只查询需要的列，永远不要用*。
1.一般，where条件越多，条目越少，速度越快。
2.ORACLE采用自下而上的顺序解析WHERE子句,根据这个原理,表之间的连接必须写在其他WHERE条件之前, 那些可以过滤掉最大数量记录的条件必须写在WHERE子句的末尾.
3.inner join比left join快很多。
4.条目多的表(不管是参照表或目的表)千万不要用for all entries.用st05跟踪会发现该语句会分成多条(海量)。如果不用for all entries,一条语句即可。
5.查询数量多也会影响速度。
6.distinct也会影响速度。
7.对某个字段建索引会加快取数速度。
8.读取内表数据要先sort,再binary search.

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