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Compare Tableau blending, joins, and filters

Last updated: Mar 29, 2026

Quick Overview

This question evaluates a candidate's competency in Tableau data integration and visualization, specifically assessing understanding of joins versus blends, filter order of operations, aggregation and null-handling behavior, level-of-detail impacts, and cross-database/calculation limitations.

  • hard
  • TCS
  • Analytics & Experimentation
  • Data Scientist

Compare Tableau blending, joins, and filters

Company: TCS

Role: Data Scientist

Category: Analytics & Experimentation

Difficulty: hard

Interview Round: Technical Screen

You have two datasets to analyze in Tableau. Primary data source: Orders - Columns: OrderID, State, Category, Sales - Rows: 1) (O1, CA, Furniture, 100) 2) (O2, CA, Office Supplies, 200) 3) (O3, NY, Technology, 150) 4) (O4, TX, Furniture, 300) 5) (O5, CA, Technology, 50) Secondary data source: Targets - Columns: State, Category, MonthlyTarget - Rows: A) (CA, Furniture, 500) B) (CA, Technology, 400) C) (NY, Furniture, 250) D) (FL, Technology, 600) Answer the following precisely: 1) If you perform a physical inner join on State and Category, which rows remain and what are the values of SUM(Sales) and SUM(MonthlyTarget) by State, Category? Repeat for a left join (Orders → Targets). 2) If instead you blend the Targets source into Orders (Orders = primary), explain exactly how Tableau computes the view when you place State and Category on rows and SUM(Sales), SUM(MonthlyTarget) on columns. Specify how unmatched members (e.g., NY–Technology; TX–Furniture; FL–Technology) appear, and whether their targets/sales show as null/zero. Why? 3) Show how the results change under each of these filters and explain why based on Tableau’s order of operations: (a) a dimension filter Category = 'Furniture' from the Orders source; (b) a dimension filter Category = 'Furniture' from the Targets source; (c) a context filter State = 'CA' on Orders; (d) a measure filter SUM(Sales) > 150 applied to the view; (e) a data source filter on Targets keeping only Category IN ('Furniture','Technology'). 4) Describe two pitfalls where blending and joining yield different aggregates due to level of detail and many-to-many relationships (e.g., duplicate State–Category rows in Targets). Provide a concrete example from the given data. 5) When would you prefer blending over joining in Tableau? Discuss cross-database analysis, required granularity, the linking field behavior, impacts on performance/caching, and limitations with calculations (e.g., FIXED LODs, table calcs) in secondary sources.

Quick Answer: This question evaluates a candidate's competency in Tableau data integration and visualization, specifically assessing understanding of joins versus blends, filter order of operations, aggregation and null-handling behavior, level-of-detail impacts, and cross-database/calculation limitations.

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TCS
Oct 13, 2025, 9:49 PM
Data Scientist
Technical Screen
Analytics & Experimentation
2
0

Tableau Integration Exercise: Joins vs Blends, Filters, and Order of Operations

Data

You have two sources.

Primary (Orders)

  • Columns: OrderID, State, Category, Sales
  • Rows:
    1. (O1, CA, Furniture, 100)
    2. (O2, CA, Office Supplies, 200)
    3. (O3, NY, Technology, 150)
    4. (O4, TX, Furniture, 300)
    5. (O5, CA, Technology, 50)

Secondary (Targets)

  • Columns: State, Category, MonthlyTarget
  • Rows: A) (CA, Furniture, 500) B) (CA, Technology, 400) C) (NY, Furniture, 250) D) (FL, Technology, 600)

Tasks

  1. Physically join Orders ↔ Targets on State AND Category.
    • Inner join: Which rows remain? What are SUM(Sales) and SUM(MonthlyTarget) by State, Category?
    • Left join (Orders → Targets): Which rows remain? What are SUM(Sales) and SUM(MonthlyTarget) by State, Category?
  2. Data blending: Use Orders as Primary and Targets as Secondary. Link on State and Category.
    • With State and Category on Rows, and SUM(Sales) and SUM(MonthlyTarget) on Columns, explain exactly how Tableau computes the view.
    • Specify how unmatched members appear (e.g., NY–Technology; TX–Furniture; FL–Technology) and whether targets/sales show as null or zero. Explain why.
  3. Show how the results change under each filter and explain why using Tableau’s order of operations.
    • (a) Dimension filter Category = 'Furniture' from Orders (primary)
    • (b) Dimension filter Category = 'Furniture' from Targets (secondary)
    • (c) Context filter State = 'CA' on Orders
    • (d) Measure filter SUM(Sales) > 150
    • (e) Data source filter on Targets keeping only Category IN ('Furniture','Technology')
  4. Describe two pitfalls where blending and joining yield different aggregates due to level of detail and many-to-many relationships (e.g., duplicate State–Category rows in Targets). Provide a concrete example based on the given data.
  5. When would you prefer blending over joining in Tableau? Address cross-database analysis, required granularity, linking-field behavior, performance/caching, and calculation limitations (e.g., FIXED LODs, table calcs) in secondary sources.

Solution

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