>Thank you, Svein. I think I will implement the "Default" solution since my application
>allows the end user to create ad-hoc queries (of sorts). I think setting the default will
>produce fewer questions about why records are omitted. You are correct in
>assuming that <unknown> is the same as empty.
>
>Would there be a problem in using Coalesce(...) in addition to setting the default
>values? I can't think of any, other than it may be overkill.

Well, using

SELECT Coalesce(FirstName, '')
FROM WorldTelephoneDirectory
WHERE Coalesce(FirstName, 'Homer') = 'Homer'

would do a natural scan, whereas

SELECT Coalesce(FirstName, '')
FROM WorldTelephoneDirectory
WHERE FirstName = 'Homer' or FirstName is NULL

might use an index. Other than that, the only thing I can think of would be to name your column, e.g.

SELECT Coalesce(FirstName, '') as FirstName

So, no real pitfalls, COALESCE is quite safe and straight forward to use, I even use it in JOIN clauses sometimes like

FROM MyMainTable MMT
LEFT JOIN MyFirstOptionalTable MFOT ...
LEFT JOIN MySecondOptionalTable MSOT ...
JOIN RequiredTable RT on RT.MyField = coalesce(MFOT.PrimaryKeyField, MSOT.PrimaryKeyField)

HTH,
Set