Free Test Complex Queries (Join,... – Databas...

Q1: Which SQL keyword is used to combine rows from two or more tables based on a related column?

A. JOIN B. UNION C. INTERSECT D. MERGE

Q2: What type of join returns only rows with matching values in both tables?

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

Q3: Which join returns all rows from the left table and matching rows from the right table?

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

Q4: What does a RIGHT JOIN return?

A. All rows from the right table and matched rows from the left table B. All rows from the left table C. Only matching rows D. All rows from both tables

Q5: What is the purpose of a FULL OUTER JOIN?

A. Returns all rows when there is a match in one of the tables B. Returns only matching rows C. Returns rows from the left table only D. Returns rows from the right table only

Q6: Which operator is used to combine the results of two SELECT statements?

A. UNION B. JOIN C. INTERSECT D. DISTINCT

Q7: What does the EXISTS keyword do in a subquery?

A. Checks if the subquery returns any rows B. Counts rows in subquery C. Returns all rows D. Deletes rows

Q8: Which subquery type is executed once and its result used by the outer query?

A. Scalar subquery B. Correlated subquery C. Non-correlated subquery D. Nested subquery

Q9: What is a correlated subquery?

A. A subquery that depends on the outer query B. A subquery that executes independently C. A subquery in a FROM clause D. A subquery that deletes rows

Q10: Which SQL clause is used to filter rows after aggregation?

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

Q11: How do you write a subquery in the WHERE clause?

A. WHERE column IN (SELECT ...) B. WHERE column = SELECT ... C. WHERE IN SELECT ... D. WHERE column SELECT ...

Q12: What is the difference between UNION and UNION ALL?

A. UNION removes duplicates, UNION ALL includes duplicates B. UNION includes duplicates, UNION ALL removes duplicates C. No difference D. UNION ALL sorts results

Q13: Which join produces a Cartesian product?

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

Q14: Which SQL keyword is used to combine columns from multiple tables?

A. JOIN B. UNION C. SELECT D. WHERE

Q15: What is the purpose of the alias in a SQL query?

A. To give a table or column a temporary name B. To permanently rename a table C. To delete a table D. To sort the result set

Q16: Which join keyword returns only the rows with no matching rows in the other table?

A. ANTI JOIN (NOT EXISTS) B. INNER JOIN C. LEFT JOIN D. RIGHT JOIN

Q17: What does the IN keyword do in a subquery?

A. Checks if a value matches any value in a list returned by subquery B. Checks for NULL C. Checks for empty sets D. Joins two tables

Q18: What is the result of this query: SELECT * FROM A JOIN B ON A.id = B.id?

A. Rows from A and B with matching ids B. All rows from A only C. All rows from B only D. Cartesian product of A and B

Q19: Which clause limits the number of rows returned?

A. LIMIT B. OFFSET C. FETCH D. WHERE

Q20: How can you refer to a table with a shorter name in a query?

A. By using an alias with AS B. By renaming the table permanently C. By creating a new table D. By dropping the original table

Quiz for Complex Queries (Join, Subqueries)