What are Aggregate tables

Aggregate tables contain redundant data that is summarized from other data in the warehouse.

These are the tables which contain aggregated / summarized data. E.g Yearly, monthly sales information. These tables will be used to reduce the query execution time.

Aggregate table contains the  summary of existing warehouse data which is grouped to certain levels of dimensions.Retrieving the required data from the actual table, which have millions of records will take more time and also affects the server performance.To avoid this we can aggregate the table to certain required level and can use it.This tables reduces the load in the database server and increases the performance of the query and can retrieve the result very fastly.

Aggregate table contains the summary of existing warhouse data , it contains data which is group accordingly (month , quartely etc) depending upon the business needs.For example you may contain transaction in fact table for all the customers but sometime you want the sum of amount for a particular customer over a month in that case you need to run the query in fact table which contains millions of row and time consuming. so avoid this problem we do the aggregation of amount in aggregate over a month for each customers, so this will improve the performance and you can retrieve the result very fastly.

Aggregate table contains summarised data. The materialized view are aggregated tables.