dynamic query

[Stephen Lime]

You can change most mapserver parameters, including class expressions on the
fly using form variables. Syntax is terse you most likely you'd have to use some
javascript to format things. So for example to change a class you'd use syntax
like:

  map_cities_class_0_expression=new expression

where 

  - map_cities_class_0_expression = form variable most like build with help of javascript
  - new expression = expression that conforms to mapserver requirements for mapfiles

The alternative is to use mapscript. One nice alternative would allow CGI substitutions
in addition to attribute substitutions. In that case you might have a CGI var called 'pop1'
and then could write an expression like ([population] > [pop1]) where one comes from 
the attribute table, the other from the user. I like that and will look into it, perhaps for 3.3.012.

Steve

Stephen Lime
Internet Applications Analyst

Minnesota DNR
500 Lafayette Road
St. Paul, MN 55155
651-297-2937

>>> Ricardo Wagner Martins <ricmar at pro.via-rs.com.br> 10/04/00 11:43AM >>>
Hi all,

How can I do a dynamic statement in a CLASS-object
in the map-file?
There seem to be only static values possible in use
with EXPRESSION like this one:

LAYER
  NAME cities # the CGI-relation

  ...

  CLASSITEM  'population' #something like this

  CLASS
   EXPRESSION ([POPULATION] > 10000)
     ....
   COLOR #e.g. red
  END

  CLASS
     EXPRESSION ([POPULATION > 50000)
     ...
     COLOR # e.g. dark red
  END
END

I wanted to use dynamic (CGI-input) values
instead of fixed values. How can I do it
here or is this just the wrong way to solve
a problem of dynamic input? Any help is
welcome and appreciated.

Ricardo Martins
PROCERGS
BRAZIL