Data Blending in Tableau

What is Data Blending?

Data Blending in Tableau is a method of combining data from multiple sources without physically merging them into a single dataset. It allows you to create visualizations using data from different databases, files, or sheets without performing joins at the database level.

Example Scenario

Imagine you have:

• Sales Data in MySQL

• Customer Demographics in an Excel file

Since they are stored in different sources, joins won’t work directly. Instead, you can use Data Blending to connect and analyze them together.

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How Does Data Blending Work?

Tableau treats one data source as the Primary Data Source and the other(s) as Secondary Data Sources. It links the two datasets using a common field (key column), known as a blending key.

Steps to Blend Data in Tableau:

1. Connect to multiple data sources in Tableau.

2. Create a visualization using fields from one Primary Data Source.

3. Drag fields from another data source (Tableau will automatically detect relationships).

4. A link icon (🔗) appears next to the related field in the Secondary Data Source.

5. Tableau blends the data dynamically using a left join-like approach at the visualization level.

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Types of Data Blending in Tableau

1. Automatic Blending

If both datasets have a common field with the same name, Tableau automatically detects and links them.
Example: If Sales Data and Customer Data both contain a field named Customer_ID, Tableau will link them automatically.

2. Manual Blending

If the field names are different or multiple fields need to be used as keys, you must manually define relationships.
Example: If one dataset has Cust_ID and the other has CustomerNumber, you must manually link them.

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Data Blending vs. Joins vs. Relationships

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When to Use Data Blending?

• When combining data from different databases (e.g., SQL + Excel).

• When you cannot use joins due to granularity differences.

• When relationships do not work, but data needs to be analyzed together.