DA0-002 Data Concepts and Environments Practice Question
A data engineer needs to extract data from a REST API and load it into a data warehouse. The data is received in JSON format. Which data type best describes JSON?
⚠ Common exam trap
A common mix-up: candidates confuse the presence of structure (keys and values) with being fully structured, overlooking that JSON lacks a fixed schema and allows variability, which places it in the semi-structured category.
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
✓
Semi-structured
JSON (JavaScript Object Notation) is classified as a semi-structured data type because it uses a flexible, self-describing schema with key-value pairs and nested structures, but does not enforce a rigid tabular schema like relational databases. In the context of extracting data from a REST API, JSON allows for varying fields and hierarchical data, which aligns with the semi-structured category.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Transactional
Why it's wrong here
Transactional describes a processing pattern with ACID guarantees, not a data format, so it does not classify JSON. It is tempting because API-sourced data often feeds transactional systems, and transactional would be correct when describing workloads requiring atomic commits, not the JSON payload itself.
- ✓
Semi-structured
Why this is correct
JSON is semi-structured: it encodes hierarchical key-value pairs and arrays without a fixed relational schema, yet retains tags and nesting that allow parsing. This distinguishes it from fully unstructured text and from rigidly structured tabular formats.
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Unstructured
Why it's wrong here
JSON has a defined schema of keys and values, so classifying it as unstructured ignores that parseable structure. It is tempting because JSON lacks a fixed relational schema and varies between API responses, and unstructured would be correct for free text, images or audio with no defined field structure.
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Structured
Why it's wrong here
JSON is semi-structured: it has hierarchical keys but no fixed relational schema, so calling it structured overstates its rigidity. It is tempting because JSON parses into typed fields, and structured would be correct for data already conforming to a fixed table schema, such as CSV or database rows.
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