Need help to join 2 layers

[beny santoso]

Dear All,

I need help to join my layers (parcel base as polygon layer) in Oracle
Spatial using mapscript.
I have 2 layers
 a. Map1 with primary key Id1
 b. Map2 with primary key Id2

I want to join this layer, so when i click  a polygon then i can show
up information in Map1 and
Map2 in one popup window.

My problem is : how to join 2 layers (in sql queries) ?
For information, that's two layers have many to many relationship.
Map1 may have equal, covers, coveredby or  overlap or maybe intersect
with Map2. So do Map2.

Thank's for any help.

Regards,

Beny