case statement to cath nulls on joined tables

Hello,

I am doing a left outer join between a polygon table and a data table.
Everything
returns fine from this join as expected. However, there are cases where
there isn?t data for a given polygon and this return as the expected null
in the result set. I would like to utilize something like a case statement
to catch the nulls and return a ?more friendly? message. I have tried
unsuccessfully to use the following logic:

*Select case value_of_interest null then ?more friendly message? else
value_of_interest end*

*From poly_table left outer join data_table one poly_table.common_id =
data_table.common_id*

If someone could let me know where I am going wrong it would be greatly
appreciated.

Cheers,

Derek