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List of 'missing' species

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List of 'missing' species

by jimmcintosh » Tue Oct 16, 2012 10:17 am

1. Does anyone know if it is possible to easily obtain a list of species which are recorded in surrounded squares* but not in a central square using the DDB?
*Whether Hectads, Tetrads or Monads.

2. In a similar vein is it possible to obtain a list of species recorded before 2000 (say) but not post 1999 in any particular square? How do you do it?
Jim
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Re: List of 'missing' species

by admin » Wed Oct 17, 2012 3:45 pm

Hi Jim,

The adjacent square query isn't possible as a general solution yet. But you could set up a search for adjacent squares and subtract the central square from that.

Image

The above would give a list of taxa not present in SD59 but present in an adjacent square (SD49,NY50,SD69,SD58). The logic is a bit convoluted, the first part of the query searches for records from the surrounding squares and groups them by species (because a taxon list rather than individual records are wanted).

This is joined with a sub-query of records from SD59. This set is joined by 'species' so only the resulting taxon list from the sub query matters. The subquery results are excluded ('exclude' is ticked).

The result is a list of taxa from the surrounding squares, except for anything that also appears in the central square.
Tom Humphrey
Database Officer, Botanical Society of Britain and Ireland (BSBI)
c/o Centre for Ecology and Hydrology,Maclean Building, Crowmarsh Gifford, Wallingford, Oxon, OX10 8BB, UK.
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Re: List of 'missing' species

by admin » Wed Oct 17, 2012 3:49 pm

The second problem, to obtain a list of taxa recorded prior to but not after a date is similar:

Image

The difference is that the set being excluded in the sub-query are records from 2000 onwards. Note that SD59 needs to be specified in both parts of the query.
Tom Humphrey
Database Officer, Botanical Society of Britain and Ireland (BSBI)
c/o Centre for Ecology and Hydrology,Maclean Building, Crowmarsh Gifford, Wallingford, Oxon, OX10 8BB, UK.
tom.humphrey@bsbi.org
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