Problem with numeric and operators

 Hi all.

 I have a problem with data type 'numeric'. If I have a field of type
 'numeric' (in this case 'foo') and execute next query:

     select * from table_example where foo > 2.45

 I get error:

     ERROR:  Unable to identify an operator '>' for types 'numeric' and 'float8'
    You will have to retype this query using an explicit cast

 What is the meaning of this? Is it a bug? What am I doing wrong?...

 Thanks.

                 David