oracle忽略大小写

You can use ALTER SESSION statements to set comparison to case-insensitive. See this FAQ.

alter session set NLS_COMP=ANSI;
alter session set NLS_SORT=BINARY_CI;

For all those visiting 8 years after this original answer has been accepted (for 10gR2):

After 10gR2, the NLS_COMP setting must be `LINGUISTIC':

ALTER SESSION SET NLS_COMP=LINGUISTIC;