[mapserver-users] Query Layer out of DB

[Stephen Lime]

Seems to me the easiest way to do this is to turn the results of the SQL query into a either an attribute query or a class expression that hilites the right polys. This assumes you have a primary key between the 2 systems, a county code or something. I'd recommend the class expression option since it's the most straight forward. 3.5 has a couple of nice features that make doing this sort of thing pretty easy. Basically you set up a map with 2 parts, layer descriptions that compose the background of the map and a single layer to use in displaying the right countries. That single layer is what you manipulate the class expression for. Set the status to OFF for that layer and set up a class like:

CLASS
  EXPRESSION /%codelist%/
  ...
END

Then in your other app you'd create a variable that cats all the country codes together (i.e. id1|id2|id3) called codelist. MapServer CGI will substitute the value of codelist for %codelist% and there you have it, a dynamic expression. Be sure to turn the layer on.

No need to go to MapScript on this one...

Steve 

Stephen Lime
Data & Applications Manager

Minnesota DNR
500 Lafayette Road
St. Paul, MN 55155
651-297-2937
>>> Alexander Pucher <pucher at atlas.gis.univie.ac.at> 09/26/01 07:11 AM >>>
Hello,

I want to explain my question with a little example.

Let's presume, I have a map of Europe with all the european countries 
included. In addition to that, I have statistical data about the various 
countries - like population, area etc. - stored in a database system - 
say MySQL. I make a SQL query, showing me the 3 countries with the 
highest poulation figures (e.g. Germany, France, UK). The system gives 
me a button saying "Show in Mapserver". What I want to see is the map of 
Europe with the three countries hilited.

I'm quite sure that this has to be done with a newLayerObj, that is 
simply put onto the "standard" layers. Can anybody give me some more 
detailed information about this. Any suggestions, code snippets, links 
or previously posted messages to mapserver-users-group would be great.

mfg
ALEX 

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Institut fuer Geographie und Regionalforschung
Universität Wien
Kartografie und Geoinformation

Departement of Geography and Regional Research
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Cartographie and GIS

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