Mapserver <-> SDE Joins

[Howard Butler]

At 02:20 PM 6/22/2006, Adam Quiney wrote:
>Hi all,
>
>We're putting together an application that uses Mapserver to connect to
>an ArcSDE instance running against an SQLServer back-end.
>
>Are joins (i.e.
>http://mapserver.gis.umn.edu/docs/reference/mapfile/join) supported with
>ArcSDE connections?  I know the ArcSDE page says "on-the-fly" joins are
>not supported, but I wasn't sure if those referred to the same thing or
>some other SDE-specific join?

on-the-fly joins means using the JOIN directive like is possible for 
Shapefile and MyGIS drivers.


>We are currently storing a set of address points in our database.  We
>also have a many-to-one relationship between these address points and
>any number of aliases that they could hold.  We would like to be able to
>perform a join between each address point and all of its aliases.  Is
>this possible on mapserver's end, or are we limited to creating a view
>in SDE that will support this?

SDE views are going to be the only way this can be done in MapServer 
currently.  All of the other native database drivers in MapServer 
provide joins by virtual of having interfaces that behave like real 
databases, rather than the database abstraction stuff that the SDE 
SDK attempts to make.  I haven't been able to find a need to develop 
JOIN support for SDE because views were always sufficient in the 
instances where I needed them.


>Lastly, if this *can* be done in mapserver, is it possible to flatten
>out the aliases so that the final feature that is displayed to the
>browser (and that would be queried upon a get-feature-info request)
>would have all of the attributes of the address point, along with an
>attribute for each attached alias (the alternative being that we have
>one address point/alias feature for each address point and alias pair).

Another advantage of using an SDE view is that you can control this 
when creating it.

Howard