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Derived Aggregation
The simplest way to define aggregations of columns in an object is to derive this information from metadata in the
database. The only objects with this information are calculation views and analytic views. For all other object
types, for example, tables and SQL views, the activation will not work. To cause the service to use derived
information, you must specify the keywords aggregates always, as illustrated in the following example:
service {
"sample.odata:calc.calculationview" as "CalcView"
keys generate local "ID"
aggregates always;
}
Explicit Aggregation
The example for the explicit aggregation is based on the following table definition:
sample.odata:revenues.hdbtable
table.schemaName = "ODATASAMPLES";
table.tableType = COLUMNSTORE;
table.columns = [
{name = "Month"; sqlType = INTEGER; nullable = false;},
{name = "Year"; sqlType = INTEGER; nullable = false;},
{name = "Amount"; sqlType = INTEGER; nullable = true;}
];
table.primaryKey.pkcolumns = ["Month","Year"];
You can aggregate the columns of objects (without metadata) that are necessary for the derivation of aggregation
by explicitly denoting the column names and the functions to use, as illustrated in the following example of a
service definition: sample.odata:aggrexpl.xsodata
service {
"sample.odata:revenues.hdbtable" as "Revenues"
keys generate local "ID"
aggregates always (SUM of "Amount");
}
The results of the entity set Revenues always contain the aggregated value of the column Amount. To extract
the aggregated revenue amount per year, add $select=Year,Amount to your requested URI.
OData Parameter Entity Sets
SAP HANA calculation views and analytic views can interpret input parameters. For OData, these parameters can
be entered by using a special parameter entity set.
Parameter entity sets can be generated for both calculation views and analytic views by adding parameters via
entity to the entity:
service {
"sample.odata:calc.calculationview" as "CalcView"
keys generate local "ID"
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P U B L I C
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SAP HANA Developer Guide
Defining Web-based Data Access