Function regexp_replace

Ref: http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions130.htm#SQLRF06302

Ref : https://oracle-base.com/articles/misc/regular-expressions-support-in-oracle

 
The following example examines the string, looking for two or more spaces. Oracle replaces each occurrence of two or more spaces with a single space.

SELECT
  REGEXP_REPLACE('500   Oracle     Parkway,    Redwood  Shores, CA',
                 '( ){2,}', ' ') "REGEXP_REPLACE"
  FROM DUAL;

REGEXP_REPLACE
--------------------------------------
500 Oracle Parkway, Redwood Shores, CA

select regexp_replace('East Champaran', '[^A-Za-z]', '') from dual;

Results 

-----------------

EastChamparan