Select ... From ... Where ... - ObjectVision/GeoDMS GitHub Wiki

Relational model versus Semantic arrays DML

The Select ... From ... Where ... statement is used to select records from a table/view that meet the condition defined in the Where Clause.

In the GeoDMS first a new domain unit needs to be configured with the e.g. the subset function, resulting in a subitem called Nr_OrgEntity with as values unit the index numbers of the original domain. This Nr_OrgEntity attribute can be used to get the data from the original domain for the new subset domain, using the lookup function (see examples).

Assume the following SQL Statement:

Select Street, Number, Zipcode, Town From Appartment Where Town = 'BTown'

This statement can be applied on our Relational model versus Semantic arrays, resulting in the following data:

GeoDMS configuration (the Appartment domain unit is configured in a src container):

unit<uint32> singleAttSelection := 
   select_with_attr_by_cond(
      DDL_Create/Apartment
     ,DDL_Create/Apartment/Town == 'BTown'
   );

In the example the select_with_attr_by_cond function is used to select elements from the DDL_Create/Apartment domain unit. The part with_attr in the function name indicates all attributes from the first argument (DDL_Create/Apartment) become available for the selection domain. The condition is configured as second argument.

Other selection functions can also be used.

Assume the following SQL Statement:

Select Street, Number, Zipcode, Town From Appartment Where ZipCode = 'AA6681' And Number = 3

This statement can be applied on our relation model, resulting in the following data:

GeoDMS configuration (the Appartment domain unit is configured in a src container):

unit MultipleAttSelection := 
   select_with_attr_by_cond(
      DDL_Create/Apartment
     ,DDL_Create/Apartment/ZipCode == 'AA6681' && DDL_Create/Apartment/Number == 3
   );