SQL Quiz

Which SQL clause is used to filter records after a GROUP BY operation?

• WHERE

• HAVING

• FILTER

• ORDER BY

What is the purpose of a JOIN in SQL?

• To combine data from multiple tables into one result set

• To delete rows from a table

• To update data in a table

• To create a new table from existing data

What is a subquery in SQL?

• A) A query that retrieves data from a single table

• B) A query that returns a single value for use in another query

• C) A query that joins two or more tables together

• D) A query that performs complex joins

What is the result of using DISTINCT in a SELECT statement?

• Removes duplicate rows in the result set

• Groups data based on a column

• Sorts the result set in ascending order

• Limits the number of rows returned

What does the RANK() window function do?

• It assigns a unique rank to each row in a result set, without ties.

• It assigns a rank based on the order of the rows, with ties given the same rank.

Which of the following is true about UNION in SQL?

• UNION returns only the distinct records from both queries

• UNION returns all records from both queries, including duplicates

• UNION requires the same number of columns and data types in both queries

• UNION does not allow sorting of the result set

What is the effect of the GROUP BY clause?

• It filters rows based on conditions

• It combines rows that have the same values into summary rows

• It sorts the result set in ascending order

• It limits the number of rows returned

How would you prevent a NULL value from being included in a COUNT() aggregation?

• Use COUNT(*)

• Use COUNT(DISTINCT column_name)

• Use COUNT(column_name) and filter NULL values in the WHERE clause

• Use COUNT(column_name) and filter NULL values in the HAVING clause

Which of the following is correct about INNER JOIN?

• It returns only the rows that exist in both tables involved in the join

• It returns all rows from both tables, even if they do not have matching rows

• It can only be used with two tables

• It combines rows with matching values in one of the tables

Which statement will create an index on a table in SQL?

• CREATE INDEX index_name ON table_name;

• CREATE TABLE index_name ON table_name;

• ADD INDEX index_name ON table_name;

• CREATE PRIMARY KEY index_name ON table_name;