DA0-002 Data Concepts and Environments Practice Question
A data analyst needs to combine customer data from a MySQL transactional database with product data from a MongoDB document store to create a unified view for reporting. The analyst uses a SQL query that joins the tables after extracting data from both sources. Which database concept is being applied?
⚠ Common exam trap
Test-takers frequently confuse a 'view' with a cross-source join, thinking a view can span multiple databases, but a view is limited to a single database and cannot directly reference tables from different database systems like MySQL and MongoDB.
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
✓
Join
(Join) because the scenario describes combining data from two different sources—MySQL and MongoDB—into a unified view using a SQL query that joins the tables after extraction. This is a classic example of a cross-source join, where data from disparate databases is merged based on a common key, which is the fundamental purpose of a JOIN operation in SQL.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
View
Why it's wrong here
Views are virtual tables based on a query, but the scenario describes an ad-hoc join.
- ✓
Join
Why this is correct
Joins combine rows from two or more tables based on a related column.
- ✗
Stored procedure
Why it's wrong here
Stored procedures are precompiled SQL statements, not applicable to cross-source joining.
- ✗
Index
Why it's wrong here
Indexes speed up data retrieval but are not used to combine data.
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