On 25 Sep 2007, at 16:39, Adam wrote:

> There is a difference in definition between null and ''. Before making
> your decision, download the 'Firebird Null Guide' from here:
> http://www.firebirdsql.org/index.php?op=doc
>
> In a nutshell, use empty when you know the value, and the value is ''.
> Use null when you don't know the value. There are certainly
> implications with respect to comparisons, uniqueness and
> concatenations just to name a few. You also need to be aware that some
> older UDF libraries may not handle null well.
>
> So it is really important you understand your data and use the right
> tool for the right job.

We have also found that users of Excel tend to assume that empty
numeric columns are actually 0.0, so make sure you understand your
numeric semantics as well. FWIW, Jet (the SQl interface to Excel)
treats these cases as NULL.
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