DBMS-Select Statement

Consider the following query:

SELECT COUNT(*) FROM employees;

What does this query return?

• The number of employees in the "employees" table.

• The names of all employees in the "employees" table.

• The average salary of employees.

• An error because COUNT(*) is not a valid function.

Consider the following query:

SELECT first_name || ' ' || last_name AS full_name FROM employees WHERE department_id = 30;

What does this query return?

• The first name of all employees in department 30.

• The last name of all employees in department 30.

• The full name (concatenation of first and last names) of employees in department 30.

• An error because the concatenation operator (||) is not allowed.

Consider the following query:

SELECT AVG(salary) FROM employees GROUP BY department_id;

What does this query return?

• The average salary of all employees.

• The average salary for each department.

• An error because you cannot use AVG() with GROUP BY.

• The total salary for each department.

Consider the following query:

SELECT employee_id, last_name FROM employees WHERE salary > 50000;

What does this query return?

• All employee IDs and last names.

• All employee IDs and last names of employees with a salary greater than $50,000.

• An error because employee_id is not a valid column.

• All employees with a salary greater than $50,000.

Consider the following query:

SELECT DISTINCT department_id FROM employees;

What does this query return?

• A list of all unique department IDs.

• A list of all department IDs, including duplicates.

• An error because DISTINCT cannot be used with SELECT.

• A list of all employee IDs.

Consider the following query:

SELECT employee_id, salary * 12 AS annual_salary FROM employees;

What does this query return?

• The monthly salary of all employees.

• The annual salary (12 times the monthly salary) of all employees.

• An error because you cannot use arithmetic operations in SELECT.

• The sum of all annual salaries.

Consider the following query:

SELECT department_id, COUNT(*) FROM employees GROUP BY department_id HAVING COUNT(*) > 5;

What does this query return?

• The number of employees in each department.

• An error because HAVING cannot be used with COUNT(*).

• The number of departments with more than 5 employees.

• The department IDs with more than 5 employees.

Consider the following query:

SELECT last_name FROM employees WHERE last_name LIKE 'S%';

What does this query return?

• The last names of all employees.

• The last names of employees whose last name starts with 'S'.

• An error because LIKE cannot be used with SELECT.

• The last names of employees whose last name contains 'S'.

Consider the following query:

SELECT department_id, MAX(salary) FROM employees GROUP BY department_id;

What does this query return?

• The maximum salary in the entire employees table.

• The maximum salary for each department.

• An error because MAX() cannot be used with GROUP BY.

• The sum of maximum salaries.

Consider the following query:

SELECT first_name, last_name FROM employees ORDER BY last_name ASC, first_name DESC; What does this query return?

• All employee names in ascending order of last name and descending order of first name.

• All employee names in descending order of last name and ascending order of first name.

• An error because you cannot use both ASC and DESC in one query.

• All employee names in random order.