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Oracle Troubleshooting

ORA-01843: not a valid month


When performing some SQL on a table the following error is returned:

ORA-01843: not a valid month


This error means that a date was used in the SQL but that Oracle did not consider the month to be a valid month.


  • If the month was expressed as a digit then try expressing it in full, i.e. January, February, etc or as a recognised abbreviation Jan, Feb, etc
  • Consider changing the session's date format, e.g.:

    alter session set nls_date_format='DD/MM/YYYY';

    However, be aware that this may have an undesirable knock-on affect for any other SQL.

This page represents one page of many pages of notes I made whilst working with Oracle 7 through to 10i. I now no longer work with Oracle databases, but hope that these notes will continue to be of benefit to others.

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