Quiz for CROSS JOIN

Q1: What does a CROSS JOIN return?

A. Only NULL values B. A Cartesian product of two tables C. All unmatched rows D. Only rows with primary key match

Q2: What is the result of a CROSS JOIN between two tables A (3 rows) and B (4 rows)?

A. 7 rows B. 12 rows C. 1 row D. 0 rows

Q3: Which JOIN type produces the Cartesian product of rows?

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

Q4: Does CROSS JOIN require an ON condition?

A. Yes, always B. No, never C. Only for MySQL D. Only for PostgreSQL

Q5: What is a potential drawback of using CROSS JOIN on large tables?

A. Duplicate data B. Performance issues C. Missing rows D. Incorrect results

Q6: Which of the following is a use case of CROSS JOIN?

A. Filtering rows B. Updating records C. Generating combinations D. Joining with conditions

Q7: Which SQL keyword is synonymous with CROSS JOIN?

A. UNION B. CROSS APPLY C. JOIN D. None of the above

Q8: How many rows will be returned if one table has zero rows in a CROSS JOIN?

A. 1 B. 0 C. All rows from second table D. Depends on columns

Q9: What happens if you forget to add a WHERE clause after a CROSS JOIN?

A. It performs a natural join B. It returns all matched rows C. It returns all combinations D. It fails with error

Q10: Which of these queries will return a Cartesian product?

A. SELECT * FROM A INNER JOIN B B. SELECT * FROM A CROSS JOIN B C. SELECT * FROM A LEFT JOIN B D. SELECT * FROM A RIGHT JOIN B

Q11: What is a Cartesian product in SQL?

A. All rows from both tables without filtering B. Matched rows from both tables C. Unique rows from both tables D. Duplicate rows from both tables

Q12: What is the output of a CROSS JOIN if table A has 5 rows and B has 0 rows?

A. 0 B. 5 C. 1 D. 5x5 = 25

Q13: How can you limit the number of results from a CROSS JOIN?

A. Use LIMIT clause B. Use ORDER BY clause C. Use HAVING clause D. Use GROUP BY

Q14: Which clause is **not** typically used with CROSS JOIN?

A. SELECT B. FROM C. ON D. LIMIT

Q15: Is CROSS JOIN commutative (i.e., A CROSS JOIN B = B CROSS JOIN A)?

A. Yes B. No C. Only in Oracle D. Depends on schema

Q16: What is the best practice before applying a CROSS JOIN?

A. Index all tables B. Remove duplicate columns C. Limit table size D. Disable triggers

Q17: Which scenario best fits using CROSS JOIN?

A. Joining employees to departments with matching IDs B. Combining all sizes with all colors for a product catalog C. Getting only related rows between two tables D. Merging datasets with shared keys

Q18: Which statement is true for CROSS JOIN in terms of data matching?

A. It only matches rows with same values B. It performs matching based on keys C. It matches all rows with all rows D. It does not perform any matching

Q19: Can CROSS JOIN be used to create test data combinations?

A. Yes B. No C. Only with WHERE clause D. Only in PostgreSQL

Q20: What will be the output of SELECT * FROM A CROSS JOIN B WHERE 1=0?

A. All rows B. No rows C. Error D. Only matched rows

Q21: How do you prevent large output from CROSS JOIN unintentionally?

A. Avoid using SELECT * B. Add WHERE clause C. Use INDEX D. Use DISTINCT