added small clarification on single-table inheritance mapper def

diff --git a/doc/build/content/mappers.txt b/doc/build/content/mappers.txt
index 70f5a1039983a6a3846eb430d903ffb69e9afe51..55642fa1e92a8f6769765ea3dcb7d70d41eca372 100644 (file)
--- a/doc/build/content/mappers.txt
+++ b/doc/build/content/mappers.txt
@@ -432,6 +432,8 @@ Single table inheritance is where the attributes of the base class as well as al
     manager_mapper = mapper(Manager, inherits=employee_mapper, polymorphic_identity='manager')
     engineer_mapper = mapper(Engineer, inherits=employee_mapper, polymorphic_identity='engineer')
 
+Note that the mappers for the derived classes Manager and Engineer omit the specification of their associated table, as it is inherited from the employee_mapper. Omitting the table specification for derived mappers in single-table inheritance is required.
+
 ##### Concrete Table Inheritance
 
 This form of inheritance maps each class to a distinct table, as below: