Removing duplicate rows: Evaluate the necessity.\n“The qualifier DISTINCT must be used in an SQL statement when we want to eliminate duplicate rows.”

Introduction / Context:
SQL provides multiple mechanisms to eliminate duplicates depending on the goal—either to return unique values in a query result or to physically deduplicate stored data. This question asks if DISTINCT is strictly required whenever we want to eliminate duplicates.

Given Data / Assumptions:

• We are talking about result sets, not necessarily physical table de-duplication.
• GROUP BY and DISTINCT both can produce unique sets in a projection.
• Window functions can help identify duplicates without removing them automatically.

Concept / Approach:
DISTINCT is a straightforward way to remove duplicate rows in the output projection. However, GROUP BY can also collapse rows to a unique set by grouping on the same columns and optionally including aggregate expressions. For physical de-duplication in a table, constraints (for example, UNIQUE) or staging logic may be used. Therefore, the statement that DISTINCT “must” be used is too strong—DISTINCT is sufficient but not necessary.

Step-by-Step Solution:

Verification / Alternative check:
Run both DISTINCT and GROUP BY versions; results match for pure deduplication without aggregations.

Why Other Options Are Wrong:

• “Correct” ignores the valid GROUP BY alternative.
• ORDER BY, views, or indexes do not make DISTINCT mandatory.

Common Pitfalls:
Using DISTINCT to hide bad joins; forgetting that GROUP BY also enforces uniqueness in the output; assuming indexes automatically remove duplicates in results (they do not).

Final Answer:
Incorrect