ORACLE文档

1.However, any performance increases achieved by adding hardware should be considered a short-term relief to an immediate problem

2。In certain circumstances, it is better to use IN rather than EXISTS. In general, if the selective predicate is in the subquery, then use IN. If the selective predicate is in the parent query, then use EXISTS.

 

转载于:https://www.cnblogs.com/anran_guojianjun/archive/2009/12/25/1632267.html