Tableau-Desktop-Found Connecting to and Preparing Data Practice Question
You are creating a data source that combines a large Sales table with a smaller Regions mapping table. You want to ensure that only rows from the Sales table that have a corresponding match in the Regions table are kept. Which join type should you use?
⚠ Common exam trap
Candidates often default to a 'Left Join', forgetting that the question specifically mandates filtering out rows that do not have a match, which requires an 'Inner Join'.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Inner Join
An inner join is the appropriate choice when you only want to return records that have matching values in both tables. This filtering behavior is essential for cleaning data where incomplete or unmatched records could skew performance metrics or create null values that interfere with visualization aggregations, ensuring the dataset remains focused only on valid, mapped geographic regions.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Left Join
Why it's wrong here
A left join returns all rows from the left table regardless of whether there is a match in the right table. This would result in null values for regions that do not have a defined mapping, which contradicts the goal of excluding non-matching sales records from the final dataset.
- ✗
Right Join
Why it's wrong here
A right join returns all rows from the right table and matching rows from the left. This would include regions that have zero sales, which is not the stated requirement to filter the sales data based on existing regional mappings provided in the second table.
- ✓
Inner Join
Why this is correct
An inner join specifically returns only the records where the join key exists in both the primary sales table and the regions mapping table. This effectively filters out any sales transactions that cannot be associated with a valid region, satisfying the requirement to maintain data integrity through exclusion.
- ✗
Full Outer Join
Why it's wrong here
A full outer join keeps all records from both tables, inserting nulls where matches do not exist. This would retain all sales records even if they do not match a region, as well as all regions even if they have no sales, failing to perform the necessary data filtering.
About these practice questions
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JA
Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Tableau (Salesforce) exam blueprint
This Tableau-Desktop-Found practice question is part of Courseiva's free Tableau (Salesforce) certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the Tableau-Desktop-Found exam.