What is an aggregate query? why would you add the same field multiple times to an aggregate query?

Aggregate query is the process through which the grouping is made on the basis of analysis of collection of individual data/information entries. This helps in making the user understand the data better which is in groups or sub groups and efficient data usage can be made.

It is most commonly used in the database software documentation, database developer etc. The query is considered as the data that the user is looking for and database is considered aggregate.

Adding same field multiple number of times towards query because the user might need to do conditional aggregation that requires same field multiple times.