PostgreSQL SQL Query Operations Quiz

1. Which aggregate function returns the average value?

MEAN()

AVG()

AVERAGE()

CALC_AVG()

2. A correlated subquery references columns from the outer query.

True

False

3. Which operator is used to check if a value exists in a list?

IN

EXISTS

CONTAINS

WITHIN

4. NULL values are treated as equal to zero in comparison operations.

True

False

5. What does the CASE statement allow you to do in a query?

Create conditional logic in SELECT

Delete rows conditionally

Join multiple tables

Filter aggregate results

6. Which function converts text to lowercase in PostgreSQL?

LOWER()

TOLOWER()

LOWERCASE()

DOWNCASE()

7. The UNION operator combines results from two queries and removes duplicates.

True

False

8. Which clause must be used with aggregate functions like COUNT() to group results?

ORDER BY

FILTER

GROUP BY

HAVING

9. What is the result of a CROSS JOIN between two tables with 3 and 4 rows respectively?

3 rows

4 rows

7 rows

12 rows

10. A FULL OUTER JOIN returns rows that exist in either table.

True

False

11. Which clause is used to filter rows after aggregation in a SELECT query?

WHERE

HAVING

FILTER

GROUP

12. The WHERE clause filters rows before aggregation in GROUP BY operations.

True

False

13. What is the correct syntax for using LIMIT in PostgreSQL?

SELECT * FROM table LIMIT 10 OFFSET 5

SELECT * FROM table TOP 10

SELECT TOP 10 * FROM table

SELECT * FROM table FETCH 10

14. Which function returns the maximum value in a column?

HIGHEST()

MAXIMUM()

MAX()

TOP()

15. A subquery is a query nested inside another query.

True

False

16. What does the ORDER BY clause do in a query?

Groups rows by column

Sorts result rows by specified column

Filters rows based on condition

Limits the number of rows

17. Which JOIN type returns all rows from the left table and matching rows from the right table?

INNER JOIN

RIGHT JOIN

LEFT JOIN

FULL OUTER JOIN

18. What is the purpose of the DISTINCT keyword in a SELECT statement?

Remove duplicate rows

Sort results alphabetically

Filter NULL values

Limit result count

19. Which function returns the number of rows in a result set?

SUM()

COUNT()

TOTAL()

ROWS()

20. What does an INNER JOIN return?

All rows from both tables

Rows that match in both tables

All rows from the left table

Rows unique to each table

PostgreSQL Associate SQL Query Operations Quiz

1. Which aggregate function returns the average value?

2.

What first name or nickname would you like us to use?

2. A correlated subquery references columns from the outer query.

3. Which operator is used to check if a value exists in a list?

4. NULL values are treated as equal to zero in comparison operations.

5. What does the CASE statement allow you to do in a query?

6. Which function converts text to lowercase in PostgreSQL?

7. The UNION operator combines results from two queries and removes duplicates.

8. Which clause must be used with aggregate functions like COUNT() to group results?

9. What is the result of a CROSS JOIN between two tables with 3 and 4 rows respectively?

10. A FULL OUTER JOIN returns rows that exist in either table.

11. Which clause is used to filter rows after aggregation in a SELECT query?

12. The WHERE clause filters rows before aggregation in GROUP BY operations.

13. What is the correct syntax for using LIMIT in PostgreSQL?

14. Which function returns the maximum value in a column?

15. A subquery is a query nested inside another query.

16. What does the ORDER BY clause do in a query?

17. Which JOIN type returns all rows from the left table and matching rows from the right table?

18. What is the purpose of the DISTINCT keyword in a SELECT statement?

19. Which function returns the number of rows in a result set?

20. What does an INNER JOIN return?