Aggregation is the method of collecting data together based on a condition and performing analytics on the data. Aggregation is very important to make sense of data of all sizes as just having raw records of data is not that useful for most use cases.
Note
Imagine a table containing one temperature measurement per day for every city in the world for five years.
For example, if you see the following table and then the aggregated view of the same data then it is obvious that just raw records do not help you understand the data. Shown below is the raw data in the form of a table:
City | Date | Temperature |
Boston | 12/23/2016 | 32 |
New York | 12/24/2016 | 36 |
Boston | 12/24/2016 | 30 |
Philadelphia | 12/25/2016 | 34 |
Boston | 12/25/2016 | 28 |
Shown below is the average temperature per city:
City | AverageTemperature |
Boston | 30 - (32 + 30 + 28)/3 |
New York | 36 |
Philadelphia | 34 |