UNION is a supported SQL construct.

• A. True
• B. False
• C. Not specified
• D. Depends

Answer: (A)

UNION is a standard SQL set operator that combines results from two or more SELECT statements into a single result set. For UNION to work, each SELECT must return the same number of columns with compatible data types in the corresponding positions. By default, UNION removes duplicate rows; if you need to include duplicates, you can use UNION ALL instead.

Because UNION is part of the SQL standard and supported by major relational databases (such as MySQL, PostgreSQL, SQL Server, and Oracle), the statement that UNION is a supported SQL construct is true. You can typically apply a single ORDER BY to the entire combined result, and you can wrap UNIONs in subqueries to perform additional formatting or sorting as needed.

Keep in mind that mismatches in column count or types cause errors, so you’d resolve those by aligning the SELECT statements (possibly with type casting or selecting equivalent expressions).