Quiz for Subqueries in FROM Clause

Q1: Why are subqueries used in the FROM clause?

A. To update data B. To create temporary tables or derived tables C. To enforce constraints D. To change schema

Q2: What is the primary purpose of using a subquery in the FROM clause?

A. To update records B. To filter rows C. To create a derived table D. To delete rows

Q3: What is a derived table?

A. A temporary table created from a subquery B. A table from another database C. A materialized view D. A table created using SELECT INTO

Q4: Which clause uses the derived table in a query?

A. JOIN B. WHERE C. FROM D. GROUP BY

Q5: Can you use an alias for a subquery in the FROM clause?

A. Yes, it is required B. No, it is optional C. Only in MySQL D. Only in PostgreSQL

Q6: Which of the following is correct syntax for a subquery in the FROM clause?

A. SELECT * FROM (SELECT * FROM employees) B. SELECT * FROM employees (SELECT salary) C. SELECT FROM (SELECT) D. FROM (SELECT)

Q7: Why must subqueries in the FROM clause have aliases?

A. To avoid ambiguity B. To improve performance C. To create indexes D. To allow ORDER BY

Q8: What is the role of the alias in a subquery in the FROM clause?

A. It renames the table B. It is ignored C. It is optional D. It makes the subquery usable in the outer query

Q9: Can you use JOINs with subqueries in the FROM clause?

A. Yes B. No C. Only in Oracle D. Only in subqueries in SELECT clause

Q10: Which of the following would result in an error?

A. SELECT * FROM (SELECT name FROM students) AS temp B. SELECT * FROM (SELECT name FROM students) C. SELECT * FROM students D. SELECT * FROM (SELECT name) AS temp

Q11: What kind of operations can be performed on a subquery in the FROM clause?

A. UPDATE B. SELECT and JOIN C. DROP D. ALTER

Q12: What does a subquery in the FROM clause return?

A. Multiple statements B. A result set C. A scalar value D. A stored procedure

Q13: How can you limit the number of rows in a subquery used in the FROM clause?

A. Using LIMIT in outer query B. Using LIMIT in subquery C. Using WHERE in outer query D. Using HAVING in subquery

Q14: Can a subquery in FROM clause include GROUP BY?

A. Yes B. No C. Only in Oracle D. Only in SELECT clause

Q15: When using a subquery in the FROM clause, how do you refer to its columns?

A. Using table name only B. Using alias.column_name C. Using subquery directly D. Using database.column_name

Q16: Which of these is NOT true about FROM subqueries?

A. They can have aliases B. They can use JOINs C. They must return a result set D. They can directly update data

Q17: Is it possible to nest subqueries inside the FROM clause subquery?

A. Yes B. No C. Only in MySQL D. Only in SQL Server

Q18: What happens if alias is missing in subquery in FROM?

A. Query fails B. Query runs slowly C. Query returns null D. Query still runs

Q19: Which clause typically follows a subquery in the FROM clause?

A. ORDER BY B. WHERE C. JOIN D. SELECT

Q20: What is another name for a subquery in the FROM clause?

A. Inline view B. Outer query C. Scalar subquery D. Temporary trigger

Q21: Why use subqueries in FROM rather than joining multiple base tables?

A. To improve readability and modularity B. To reduce code size C. To eliminate need for WHERE D. To avoid using indexes