Top Tableau Scenario-Based Interview Questions Set -4 (1- 6)

1. How would you fix blend errors?
   Ensure both data sources have a common linking field with matching data types and values.
   Example:

   STR([Customer ID])
   

   Convert fields to same datatype if one source has Number and another has String.

2. How would you fix duplicate marks in blended view?
   Duplicates usually happen due to different granularity in secondary source.
   Use aggregation like:

   SUM([Target Sales])
   

   or FIXED LOD:

   { FIXED [Region] : SUM([Target]) }
   

3. How would you reduce marks in scatter plot?
   Reduce dimensions and aggregate measures to minimize rendered points.
   Example:

   AVG([Sales])
   

   by Region instead of Customer-level data reduces mark count significantly.

4. How would you design mobile-friendly dashboards?
   Use Device Designer and create separate mobile layouts with fewer visuals and filters.
   Example:
   Keep only KPI cards and one chart on mobile instead of full desktop dashboard.

5. How would you secure row-level data?
   Create user-based filter logic using USERNAME() function.
   Example:

   [Region Manager] = USERNAME()
   

   Users will see only their assigned region data.

6. How would you fix incorrect totals in dashboard?
   Validate joins, aggregation level, and table calculation scope.
   Example:

   SUM([Sales])
   

   may duplicate after joins, so use:

   { FIXED [Order ID] : SUM([Sales]) }
   

   to avoid inflated totals.

Bhagavad Gita Wisdom #shorts

https://www.youtube.com/playlist?list=PLQM-BpTd9ZSumxwKgJjuJjlx2OcP_W516 

Top Tableau Scenario-Based Interview Questions Set -3 (1- 10)

 

1. How would you combine historical and current data?
   Use UNION to append both datasets having same columns.
   Example SQL:

   SELECT * FROM Sales_History
   UNION ALL
   SELECT * FROM Sales_Current
   

   In Tableau, drag one table below another to create union.

2. How would you union monthly files automatically?
   Use Wildcard Union in Tableau for files with similar structure.
   Example:

   Sales_Jan.csv
   Sales_Feb.csv
   Sales_Mar.csv
   

   Use:

   Sales_*.csv
   

   Tableau automatically combines all matching files.

3. How would you handle null values?
   Use IFNULL() or ZN() to replace nulls.
   Example:

   IFNULL([Profit],0)
   

   or

   ZN([Sales])
   

   to convert NULL into 0.

4. How would you replace missing dates in a trend chart?
   Convert date to continuous and enable “Show Missing Values.”
   Example:

   MONTH([Order Date])
   

   Then right-click axis → Show Missing Values.

5. How would you create a complete date scaffold?
   Create a calendar table containing all dates and join with fact table.
   Example SQL:

   SELECT Calendar.Date, Sales.Amount
   FROM Calendar
   LEFT JOIN Sales
   ON Calendar.Date = Sales.OrderDate
   

   This ensures all dates appear even without transactions.

6. How would you show data when no transactions exist?
   Use LEFT JOIN with dimension/scaffold table.
   Example:

   SELECT C.CustomerName, IFNULL(SUM(S.Amount),0)
   FROM Customers C
   LEFT JOIN Sales S
   ON C.CustomerID = S.CustomerID
   GROUP BY C.CustomerName
   

   Customers with no sales still appear.

7. How would you use relationship vs join?
   Use Relationships for logical layer and Joins for physical merge.
   Example:
   • Relationship keeps tables separate until query time.
   • Join physically combines rows immediately using Inner/Left Join.

8. How would you optimize a slow dashboard?
   Reduce marks, avoid unnecessary quick filters, and simplify calculations.
   Example:

   IF SUM([Sales]) > 1000 THEN "High" END
   

   Replace complex nested calculations with simpler logic.

9. How would you improve dashboard load time?
   Use extracts instead of live connection and aggregate data.
   Example:

   SUM([Sales])
   

   at Month level instead of transaction level reduces records processed.

10. How would you improve filter performance?
    Use Context Filters so Tableau processes smaller datasets first.
    Example:

• Add Region filter to Context.
• State filter now works only on selected Region data.

11. How would you optimize heavy LODs?
    Push calculations to database or simplify FIXED calculations.
    Example:

{ FIXED [Customer ID] : SUM([Sales]) }

Instead of multiple nested LODs, pre-aggregate data in SQL/ETL.

Bhagavad Gita Wisdom #shorts

https://www.youtube.com/playlist?list=PLQM-BpTd9ZSumxwKgJjuJjlx2OcP_W516