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Simple Associations
The definition of an association requires you to specify a name, which references two exposed entities and whose
columns keep the relationship information. To distinguish the ends of the association, you must use the keywords
principal and dependent. In addition, it is necessary to denote the multiplicity for each end of the
association.
Service definition: sample.odata:assocsimple.xsodata
service {
"sample.odata:customer.hdbtable" as "Customers";
"sample.odata:order.hdbtable" as "Orders";
association "Customer_Orders" principal "Customers"("ID") multiplicity
"1" dependent "Orders"("CustomerID") multiplicity "*";
}
The association in the example above with the name Customer_Orders defines a relationship between the
table customer, identified by its EntitySet name Customers, on the principal end, and the table
order, identified by its entity set name Orders, on the dependent end. Involved columns of both tables are
denoted in braces ({}) after the name of the corresponding entity set. The multiplicity keyword on each end
of the association specifies their cardinality - in this example, one-to-many.
The number of columns involved in the relationship must be equal for both ends of the association, and their order
in the list is important. The order specifies which column in one table is compared to which column in the other
table. In this simple example, the column customer.ID is compared to order.CustomerID in the generated
table join.
As a result of the generation of the service definition above, an AssociationSet named Customer_Orders
and an Association with name Customer_OrdersType are generated:
http://localhost:8002/sample/odata/assocsimple.xsodata/$metadata
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P U B L I C
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SAP HANA Developer Guide
Defining Web-based Data Access