How to test for existence of nothing

Keith Bradnam krb at sanger.ac.uk
Thu Jul 19 10:29:10 EST 2001

> Any acedb query gurus out there who can help me with a problem?
> It might be that it's beyond the capabilities of the acedb query language
> in which case Ed will set me straight.
> How do you test for the absence of a value in a tag-value pair where you
> would normally expect a value?
> Any ideas anyone?  This would be really useful to me if it is possible.

Well seeing as I've already started talking to myself, I'll continue...

As always with acedb, there is more than one way to skin a cat.
Sylvia Martinelli has just kindly pointed ou to me that the acedb
TableMaker facility can test for the presence of NULL values.  So for my
Homol tag-value problem, a tablemaker solution might me as follows:

Colonne 1 
Width 12 
Class Sequence 
>From 1 
Colonne 2 
Width 12 
>From 1 
Tag Pep_homol 
Colonne 3 
Width 12 
Class Protein 
Right_of 2 
Tag Pep_homol 

Note the 'Null' tag in the 3rd column.


~  Keith Bradnam - WormBase group: http://wormbase.sanger.ac.uk/
~  The Sanger Centre, Wellcome Trust Genome Campus
~  Hinxton, Cambridge, CB10 1SA, UK.  Tel (01223) 497516

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