Bird
0
0

Why is it important that the SELECT statements combined by set operations have the same number of columns and compatible data types?

hard📝 Conceptual Q10 of 15
SQL - Set Operations
Why is it important that the SELECT statements combined by set operations have the same number of columns and compatible data types?
ABecause it creates new tables automatically
BBecause it improves query speed
CBecause SQL needs to align columns to combine rows correctly
DBecause it allows sorting of results
Step-by-Step Solution
Solution:

  1. Step 1: Understand set operation requirements

    Set operations combine rows from queries, so columns must match in number and type to align data properly.

  2. Step 2: Explain why alignment matters

    If columns differ, SQL cannot combine rows correctly, causing errors.

  3. Final Answer:

    Because SQL needs to align columns to combine rows correctly -> Option C

  4. Quick Check:

    Column alignment = same number and type [OK]
Quick Trick: Set operations require matching columns and types [OK]
Common Mistakes:
MISTAKES
  • Thinking it affects speed only
  • Assuming new tables are created
  • Confusing with sorting requirements

Want More Practice?

15+ quiz questions · All difficulty levels · Free

Free Signup - Practice All Questions
More SQL Quizzes
Aggregate Functions - AVG function - Quiz 2easy GROUP BY and HAVING - GROUP BY single column - Quiz 5medium GROUP BY and HAVING - GROUP BY single column - Quiz 4medium INNER JOIN - INNER JOIN syntax - Quiz 8hard LEFT and RIGHT JOIN - Why outer joins are needed - Quiz 15hard LEFT and RIGHT JOIN - Finding unmatched rows with LEFT JOIN - Quiz 15hard Set Operations - UNION ALL with duplicates - Quiz 11easy Subqueries - Subquery in FROM clause (derived table) - Quiz 11easy Views - Updatable views and limitations - Quiz 10hard Views - Dropping and altering views - Quiz 1easy