Not able to left join two tables using a non numeric column? ora-01722

I would like to check, is it possible to left join two tables using a non numeric column?

i.e. where descriptions_cd is a varchar(10) and table_cd is a varchar(10):

   SELECT * 
     FROM descriptions d 
LEFT JOIN tables t ON t.table_cd = d.descriptions_cd;

This SQL seems to be giving an ora-01722 error. Th开发者_运维知识库is is in Oracle 9i.

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Can you check values of one of these column contain only numeric data (even if the volumn type is varchar) ?

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ok, table_cd is not numeric. that explains.