Quiz for UNION ALL

Q1: What is the primary difference between UNION and UNION ALL?

A. UNION ALL removes duplicates B. UNION returns all records including duplicates C. UNION ALL includes duplicates D. UNION does not include duplicates

Q2: Which operator includes all rows, including duplicates?

A. UNION B. INTERSECT C. UNION ALL D. EXCEPT

Q3: If you want to combine the results of two queries without removing duplicates, you should use:

A. INTERSECT B. UNION ALL C. UNION D. MINUS

Q4: Which of the following will return duplicate rows in the result?

A. UNION ALL B. INTERSECT C. UNION D. MINUS

Q5: Which condition must be true for using UNION ALL between two SELECT queries?

A. Only first SELECT needs ORDER BY B. Both queries must return same number of columns C. The second query must be subquery D. Column names must match exactly

Q6: Which clause is optional in a UNION ALL statement?

A. WHERE B. GROUP BY C. ORDER BY D. All of the above

Q7: How many result sets will you get from a UNION ALL of two queries returning 5 and 3 rows respectively with 2 duplicates?

A. 10 B. 6 C. 8 D. 7

Q8: Which SQL keyword is used to eliminate duplicates in combined queries?

A. INTERSECT B. UNION C. UNION ALL D. DISTINCT UNION

Q9: Which set operator is most efficient in terms of performance?

A. UNION B. UNION ALL C. INTERSECT D. MINUS

Q10: Does UNION ALL sort the result set by default?

A. Yes B. No C. Depends on DBMS D. Only if specified

Q11: Which clause can be used to order results of UNION ALL?

A. GROUP BY B. ORDER BY C. WHERE D. HAVING

Q12: Can you use WHERE clause in both queries used in UNION ALL?

A. Yes B. No C. Only in first query D. Only in second query

Q13: To filter out duplicates after UNION ALL, what must be applied?

A. DISTINCT B. GROUP BY C. HAVING D. MINUS

Q14: UNION ALL requires column datatypes in both queries to be:

A. Exact match B. Similar or compatible C. Completely different D. Only first column needs match

Q15: UNION ALL cannot be used if:

A. Column names differ B. Number of columns differs C. Datatypes differ D. Column aliases differ

Q16: In UNION ALL, duplicate rows are:

A. Always removed B. Never removed C. Removed only with GROUP BY D. Optional

Q17: When using UNION ALL, column names in final output come from:

A. First SELECT B. Second SELECT C. Both queries D. Database default

Q18: Which SQL command combines rows from two queries while preserving duplicates?

A. JOIN B. UNION C. UNION ALL D. INTERSECT

Q19: Can ORDER BY be used after UNION ALL?

A. No B. Yes, after last SELECT only C. Yes, after entire UNION ALL D. Yes, anywhere

Q20: To sort combined results in UNION ALL, use ORDER BY:

A. In each SELECT B. After UNION ALL C. Before UNION ALL D. Only inside subquery