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Expose an object using the object's repository (design-time) name in the OData service-definition file. This
method of exposing database objects by OData has the advantage that the OData service is automatically
updated if the underlying repository object changes.
● Database objects
Expose an object using the object's database catalog (runtime) name (along with the schema name). The
support for database objects is mainly intended for existing or replicated objects that do not have a repository
design-time representation.
Note: Although both declaration methods are supported, the recommended method is to use the
repository name of the object(s) you want to expose using OData.
OData Service-Definition Type Mapping
During the activation of the OData service definition, SQL types are mapped to EDM types according to a mapping
table. For example, the SQL type "Time" is mapped to the EDM type "EDM.Time"; the SQL type "Decimal" is
mapped to the EDM type "EDM.Decimal"; the SQL types "Real" and "Float" are mapped to the EDM type
"EDM.Single".
In the following example, the SQL types of columns in a table are mapped to the EDM types in the properties of an
entity type.
{name = "ID"; sqlType = INTEGER; nullable = false;}, {name = "RefereeID";
sqlType = VARCHAR; nullable = true;}
OData Service-Definition Features
The OData service definition provides a list of keywords that you use in the OData service-definition file to enable
important features. For example, the following list illustrates the most-commonly used features used in an OData
service-definition and, where appropriate, indicates the keyword to use to enable the feature:
● Aggregation
The results of aggregations on columns change dynamically, depending on the grouping conditions. As a
result, aggregation cannot be done in SQL views; it needs to be specified in the OData service definition itself.
Depending on the type of object you want to expose with OData, the columns to aggregate and the function
used must be specified explicitly (explicit aggregation) or derived from metadata in the database (derived
aggregation). Note that aggregated columns cannot be used in combination with the $filter query
parameter, and aggregation is only possible with generated keys.
● Association
Define associations between entities to express relationships between entities. With associations it is possible
to reflect foreign key constraints on database tables, hierarchies and other relations between database
objects.
● Key Specification
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SAP HANA Developer Guide
Defining Web-based Data Access