You have two tables in an ANSI-SQL compliant database with identical columns that you need to quickly combine into a single table, removing duplicate rows from the result set. What should you do?

Question

Options

• AUse the JOIN operator in SQL to combine the tables.
• BUse nested WITH statements to combine the tables.
• CUse the UNION operator in SQL to combine the tables.
• DUse the UNION ALL operator in SQL to combine the tables.

• A
  6% (2)
• B
  3% (1)
• C
  88% (29)
• D
  3% (1)

Explanation

The UNION operator in standard SQL combines the result sets of two SELECT statements into a single result set and automatically removes duplicate rows. This is exactly what the question requires: combining two tables with identical columns while deduplicating. Option D, UNION ALL, also combines result sets but retains all duplicate rows - it does not remove duplicates. Option A, JOIN, combines tables by matching rows on a condition (e.g., a key column); it does not stack rows from two tables vertically. Option B, nested WITH statements (CTEs), is a way to organize queries but is not an operator that combines tables on its own. UNION (C) is the precise ANSI-SQL operator for this task.

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