How to fetch data from multiple tables in one GET_ENTITYSET method?

Hi Experts,

Requirement is to fetch the data from three different tables and display in one single table on front end.

In single OData service i have 3 GET_ENTITYSET method for three different entity types. I want to fetch data from 3 different database tables based on key fields.

If I write select query in 3rd GET_ENTITYSET method then how i can access the 3 table's data in one method.

Thanks,

Prashant