Mastering SQL: A Student's Guide

Which SQL clause is used to filter records in a query result?

• `ORDER BY`

• `GROUP BY`

• `WHERE`

• `HAVING`

Which SQL statement is used to retrieve all columns from a table named `students`?

• `SELECT * FROM students;`

• `GET ALL FROM students;`

• `FETCH ALL FROM students;`

• `RETRIEVE * FROM students;`

What is the purpose of the `JOIN` clause in SQL?

• To delete records from a table

• To combine rows from two or more tables based on a related column

• To update records in a table

• To create a new table

Consider the following SQL query: `SELECT name FROM employees WHERE department = 'Sales';`. What does this query do?

• It selects all columns from the `employees` table where the department is 'Sales'.

• It selects the `name` column from the `employees` table where the department is 'Sales'.

• It updates the `name` column in the `employees` table to 'Sales'.

• It deletes records from the `employees` table where the department is 'Sales'.

What type of SQL join returns all records from the left table and the matched records from the right table?

• INNER JOIN

• LEFT JOIN

• RIGHT JOIN

• FULL JOIN

Michael is analyzing the employee distribution across various departments in his company. What does the following SQL query do? `SELECT department, COUNT(*) FROM employees GROUP BY department;`

• It counts the number of employees in each department.

• It adds all employees from each department showing the total.

• It updates the department count in the `employees` table.

• It deletes departments with no employees.