How to test for existence of nothing
krb at sanger.ac.uk
Thu Jul 19 04:11:18 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?
E.g. we have sequence objects with Homol tags. Associated with the Homol
tag should be the name of a Sequence object. Occasionally though, errors
creep in where we lose the object and are left with just a tag.
I would ideally like to be able to query the database to find errant
entries like this. I thought I might be able to get away with things like
Find Sequence Homol AND NEXT = ""
But (perhaps obviously) the 'AND NEXT' can't actually step any further to
the right as there is nowhere to go.
Maybe I should be looking into the dark murky world of AQL queries?
I guess I want a perl style 'if (defined($tag))' to test for the presence
(or absence) of a value for any specified tag.
Any ideas anyone? This would be really useful to me if it is possible.
~ 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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