Quiz for Single Row Subquery

Q1: Which operator is commonly used with single-row subqueries?

A. IN B. = C. ANY D. ALL

Q2: What does a single row subquery return?

A. A single row and single column B. Multiple rows and columns C. Only one column D. Only NULL

Q3: Which operator is commonly used with single row subqueries?

A. IN B. EXISTS C. = D. ALL

Q4: Which clause can use a single row subquery?

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

Q5: Which of the following is a valid single row subquery usage?

A. SELECT * FROM emp WHERE sal = (SELECT MAX(sal) FROM emp); B. SELECT * FROM emp WHERE sal IN (SELECT MAX(sal) FROM emp); C. SELECT * FROM emp GROUP BY (SELECT deptno FROM emp); D. SELECT * FROM emp WHERE sal = ALL (SELECT sal FROM emp);

Q6: What happens if a single row subquery returns more than one row?

A. It returns all rows B. It throws an error C. Only first row is used D. NULL is returned

Q7: Which of the following can cause a single row subquery to return more than one row?

A. A GROUP BY clause B. An aggregate function C. A missing WHERE clause D. A DISTINCT keyword

Q8: Which aggregate function is commonly used in single row subqueries?

A. COUNT B. SUM C. MAX D. ALL of the above

Q9: What type of comparison operator is invalid with single row subqueries?

A. = B. <= C. != D. IN

Q10: Which error is thrown if a single row subquery returns multiple rows?

A. ORA-01427 B. ORA-00936 C. ORA-00904 D. ORA-00001

Q11: Which subquery is invalid as a single row subquery?

A. (SELECT COUNT(*) FROM emp) B. (SELECT ename FROM emp WHERE deptno=10) C. (SELECT MAX(sal) FROM emp) D. (SELECT AVG(comm) FROM emp)

Q12: Which of the following clauses can include a single row subquery?

A. WHERE B. SELECT C. HAVING D. All of the above

Q13: What result will be returned if a single row subquery returns no rows?

A. NULL B. 0 C. Error D. All rows

Q14: Which of these is suitable for a salary comparison using a single row subquery?

A. sal IN (SELECT sal FROM emp) B. sal = (SELECT MAX(sal) FROM emp) C. sal > ANY (SELECT sal FROM emp) D. sal LIKE (SELECT sal FROM emp)

Q15: Which scenario best fits a single row subquery?

A. Finding highest paid employee B. Finding employees in multiple departments C. Finding all employees with bonuses D. Joining two large tables

Q16: Is the following query valid? SELECT * FROM emp WHERE sal < (SELECT AVG(sal) FROM emp);

A. Yes B. No C. Only in Oracle D. Only if AVG(sal) returns NULL

Q17: Which is true about single row subqueries?

A. They can return NULL B. They always return 1 row with value C. They work only in SELECT clause D. They use GROUP BY by default

Q18: Which clause does NOT commonly use single row subqueries?

A. WHERE B. HAVING C. SELECT D. FROM

Q19: Which is a correct single row subquery?

A. SELECT * FROM emp WHERE sal = (SELECT AVG(sal) FROM emp); B. SELECT * FROM emp WHERE sal IN (SELECT AVG(sal) FROM emp); C. SELECT * FROM emp WHERE sal = ALL (SELECT sal FROM emp); D. SELECT * FROM emp WHERE sal LIKE (SELECT sal FROM emp);

Q20: Can we use a single row subquery in the SELECT clause?

A. Yes B. No C. Only in Oracle D. Only with JOINs

Q21: Which of the following will NOT work as a single row subquery?

A. (SELECT MAX(sal) FROM emp) B. (SELECT deptno FROM emp) C. (SELECT COUNT(*) FROM emp) D. (SELECT SUM(sal) FROM emp)