Quiz for SELF JOIN

Q1: What is a SELF JOIN used for?

A. Joining two databases B. Joining a table to itself C. Joining using a subquery D. Joining NULLs only

Q2: What is a SELF JOIN in SQL?

A. A join of a table with itself B. A join of two databases C. A join using subquery D. A join using a different table

Q3: Which clause is typically used with SELF JOIN?

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

Q4: Which keyword is used to create an alias in a SELF JOIN?

A. AS B. ALIAS C. JOIN D. TABLE

Q5: Why would you use a SELF JOIN?

A. To compare rows within the same table B. To create duplicate rows C. To delete data D. To change schema

Q6: Which scenario is best suited for a SELF JOIN?

A. Finding manager-subordinate relationships in one table B. Merging two tables C. Finding maximum salary D. Creating views

Q7: Can SELF JOIN be used with INNER JOIN?

A. Yes B. No C. Only in Oracle D. Only in MySQL

Q8: What must be true for a SELF JOIN to work?

A. The table must have a related column to join on B. The table must be empty C. The table must be indexed D. The table must have a trigger

Q9: How many aliases are usually used in a SELF JOIN?

A. 2 B. 1 C. 3 D. 4

Q10: What is the purpose of table alias in SELF JOIN?

A. To distinguish between two instances of the same table B. To rename columns C. To drop columns D. To filter rows

Q11: Which of these is a correct syntax for SELF JOIN?

A. SELECT A.name, B.name FROM employee A, employee B WHERE A.manager_id = B.id; B. SELECT * FROM employee JOIN employee; C. SELECT * FROM employee; D. SELECT * WHERE employee = employee;

Q12: Which SQL join type does SELF JOIN use by default?

A. INNER JOIN B. LEFT JOIN C. RIGHT JOIN D. FULL JOIN

Q13: Can SELF JOIN be used with OUTER JOINs?

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

Q14: What does a SELF JOIN return?

A. Rows that match based on join condition within same table B. Only distinct rows C. Only NULL rows D. Only indexed columns

Q15: Is SELF JOIN limited to numeric columns?

A. No B. Yes C. Only in Oracle D. Only for foreign keys

Q16: Can a table be self-joined more than once?

A. Yes B. No C. Only twice D. Only in subqueries

Q17: What is the result of a SELF JOIN without a proper condition?

A. Cartesian product B. Error C. Zero rows D. Duplicate table

Q18: Which clause defines the relation in a SELF JOIN?

A. ON B. USING C. WITH D. AS

Q19: Can SELF JOIN be used in UPDATE statements?

A. Yes B. No C. Only in MySQL D. Only in SELECT

Q20: What is the main challenge with SELF JOINs?

A. Understanding aliases and join logic B. Syntax errors C. Slow speed D. Unsupported SQL dialect

Q21: Which of the following can benefit from a SELF JOIN?

A. Detecting duplicate rows B. Exporting data C. Creating users D. Deleting tables