While preparing for the Data Analyst certification exams, I realized there are a lot of basic but essential topics and terms that needs to be recalled. Therefore I am writing a couple of blogs to help me go through them.
On combining and modeling data source connections, Tableau provides has several options namely: relationships, joins, unions and blending. Each has its own benefits, which can be related to performance or the ability to bring data together.
Relationships leverages related fields between tables to create contextually-appropriate joins on the fly or the quickest way. This is the default data modeling option in Tableau and provides good fit for optimal performance or reducing risk of miss-aggregation, duplication and incorrect values
Joins merges tables based on a join clause to create new fixed table. This method is used to add new data column across a standard row structure. Improper joins can cause data duplication, aggregation issues and large tables. Joins will add new columns across row structure. Users should be aware of the grain and type of data that are being combined.
Union appends two or more tables to form a new combined table. This model is useful for tables with the same number of columns and data types.
Blending uses separate sources which are visualized in the same view via blended fields. The result is similar to a left join and its best for quick view level combine data source visualization. Blending have limitations but they are appropriate in some scenarios.
Choosing a method of combining data is not mutually exclusive. One can use any combination of these methods in the same workbook as long as it meets the need of the use case.