weiguo21的专栏

1.索引的坏处   索引可以加快查询xiao

做sql优化的前提瞧见是sql等价 1.MAX/MIN 的索引优化 drop table t purge; create table t as select * from dba_objects; alter table t add constraint pk1_object_id primary key (OBJECT_ID); set autotrace on set line