A user can use the groupby service call type to return common properties using the following syntax:
?$apply=groupby((Property_To_Group_By),aggregate(Id with countdistinct as Count))
When a Property_To_Group_By is a specified column item on the entry point you are querying, you can use the following example GET:
. . /api/v2/SDA/Tags?$apply=groupby((Tag_Status,Discipline),aggregate(Id with countdistinct as Count))
This example call returns all the user Tags grouped together by their Tag_Status, Discipline, and the number of objects with those properties displayed as a Count.
. . /api/v2/SDA/$metadata#Tags(Tag_status,Discipline,Count
This call is currently only available on V2.