How to get EPSG code from SRID

 I have a SRID and I need to retrieve the EPSG code based on SRID.  I got the function :

select sdo_cs.map_oracle_srid_to_epsg (82300) from dual;

but it is returning null.

 Where can I get the ESPG code ?
 What is the table name that contains it ?

Regards
Eriovaldo

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