DA0-002 Data Acquisition and Preparation Practice Question
A data analyst needs to retrieve all unique job titles from the employees table. Which SQL clause should be used with the SELECT statement?
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
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DISTINCT
The DISTINCT keyword is used to return only distinct (different) values.
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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TOP
Why it's wrong here
TOP limits the number of rows returned by a query; it does not remove duplicate values, so repeated job titles would still appear. It is used to restrict result set size, such as returning the highest-paid employees, not to produce a distinct list of values.
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UNIQUE
Why it's wrong here
UNIQUE is a constraint applied when creating an index or table column to enforce that no duplicate values are stored; it is not a SELECT clause. It is used in data definition statements to protect data integrity, not to filter duplicate rows from query output.
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DISTINCT
Why this is correct
DISTINCT removes duplicate rows from the result set, so each job title appears once. The stem explicitly requires all unique job titles, and DISTINCT operates on the selected column values, satisfying that uniqueness constraint directly. GROUP BY would also deduplicate but returns grouped aggregates rather than a simple unique list.
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ORDER BY
Why it's wrong here
ORDER BY sorts the result set by specified columns; it neither removes duplicate rows nor restricts which columns are returned. DISTINCT is the clause that eliminates duplicate job titles. ORDER BY would be the right choice when the requirement is to present retrieved rows in a defined sequence, such as alphabetical job titles.
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