Combining POINT and POLYGON Layer in mapfile

Question

I have two layers defined in a mapfile, for displaying either polygons or points dependent on a query parameter of the accessing WMS Request.

Is it possible to combine them in a UNION layer or something similar?

In a way that the WMS Request request only one Layer, not both?

Answer 1

I'm assuming by requesting "only one layer" you mean using one parameter rather than a list of "LAYERS=mylayer,mylayer2" you can use wms_layer_group and then request using "LAYERS=mygroup":

LAYER
  NAME "mylayer"
  DATA "mylayer"
  TYPE LINE
  CLASS
    STYLE
      COLOR 100 100 255
    END
  END
  METADATA
   "WMS_LAYER_GROUP" "/mygroup"
  END
END

LAYER
  NAME "mylayer2"
  DATA "mylayer2"
  TYPE POLYGON
  CLASS
    STYLE
      COLOR 100 100 255
    END
  END
  METADATA
   "WMS_LAYER_GROUP" "/mygroup"
  END