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OData Key Specification
The OData specification requires an EntityType to denote a set properties forming a unique key. In HANA only
tables may have a unique key, the primary key. For all other (mostly view) objects you need to specify a key for the
entity. In OSDL you can do this by denoting a set of existing columns or by generating a key.
For the examples illustrating key specification, we use the following SQL view, which selects all data from the
specified table.
View definition sample.odata:view.hdbview
{
}
"name": "view",
"schema": "ODATASAMPLES",
"query": "SELECT * FROM \"ODATASAMPLES\".\"sample.odata::table\""
Existing Key Properties
If the object has set of columns that may form a unique key, you can specify them as key for the entity. These key
properties are always selected from the database, no matter if they are omitted in the $select query option.
Therefore explicit keys are not suitable for calculation views and analytic views as the selection has an impact on
the result.
Service definition sample.odata:explicitkeys.xsodata/$metadata
service {
"sample.odata:view.hdbview" as "MyView" keys ("ID","Text");
}
The created metadata document for the exposure of the view above is almost equal to the metadata document for
repository objects. Only the key is different and consists now of two columns:
http://localhost:8002/sample/odata/explicitkeys.xsodata/$metadata
SAP HANA Developer Guide
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