Overview of JoinsΒΆ
Let us get an overview of joining Data Frames.
Our data cannot be stored in one table. It will be stored in multiple tables and the tables might be related.
When it comes to transactional systems, we typically define tables based on Normalization Principles.
When it comes to data warehousing applications, we typically define tables using Dimensional Modeling.
Either of the approach data is scattered into multiple tables and relationships are defined.
Typically tables are related with one to one, one to many, many to many relationships.
When we have 2 Data Sets that are related based on a common key we typically perform join.
There are different types of joins.
INNER JOIN
OUTER JOIN (LEFT or RIGHT)
FULL OUTER JOIN (a LEFT OUTER JOIN b UNION a RIGHT OUTER JOIN b)