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Posted by Peder Enhorning

September 24, 2019


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Why Do You Need a Data Warehouse or Data Mart?

We often get questions about better analytical insight and dashboard performance. We design dashboards that adhere to IPA (Insight, Performance, Appearance) but that’s often not possible if the underlying data structures are deficient and not properly organized.

Tableau connects natively to many different SOR (System of Record) data sets found in an organization. They can be from transactional databases, CRM, financial systems, Excel files, and so on. While connecting directly to visualize data in Tableau may seem more efficient, the results are often not optimal. The diagrams below illustrate the advantages and disadvantages of connecting directly to the SOR versus bringing those data sets into an OLAP (Online Analytical Processing) database, such as a Data Mart or Data Warehouse that is specifically designed for reporting and data visualization.

Tableau connected directly to data sources:


  • Faster to implement
  • Less infrastructure to manage
  • No ETL skills required for dashboard designers


  • Requires business users to understand underlying SOR database structure
  • Dashboards can be fragile if underlying databases change
  • Data blending can have poor performance
  • Requires extensive permissions across databases if there is sensitive data
  • Requires direct access from Tableau Server to SOR
  • Analysis is often less robust and complete

Tableau connected to a Data Mart which has been created from various data sources:


  • Dashboards resilient to underlying SOR changes
  • Business does not need to understand underlying SOR database structure
  • Combining data sets provides more analysis and insights
  • Data access permissions can be consolidated into a single location
  • Dashboards never go directly against SOR
  • Enterprise solution that can grow with the organization


  • Requires technical (ETL) skills to implement
  • ETL scripts require updating as underlying database changes
  • Requires planning and construction time
  • Additional infrastructure required (e.g., software, hardware)

Whether you connect directly to a data source or to a Data Mart depends on the data sources you want to use, your dashboard requirements, and available resources. If you’re not sure whether your data needs to be restructured to achieve optimal dashboard performance, a Tableau Data Specialists would be happy to answer any questions and provide a recommendation. Contact a Tableau Data Specialist

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