Which qualifier returns only unique values in a result set?

• A. From
• B. Distinct
• C. All
• D. Where

Answer: (B)

Distinct is the qualifier used to remove duplicates and return only unique values in the result set. When you write SELECT DISTINCT along with your columns, the database ensures that each row in the output is unique with respect to the selected columns. If you choose a single column, you get the distinct values from that column; if you choose multiple columns, the uniqueness is determined by the entire row formed by those columns. This happens after the data is gathered from the source tables and any filters have been applied, and before the results are ordered. The other options don’t enforce uniqueness: the source (From) just defines where rows come from; filtering (Where) selects rows that meet a condition but doesn’t remove duplicates by itself; and All would include every row, including duplicates.