Learn Aggregate Functions and Calculations

 Aggregate Functions

• Count( )
  
• Sum( )
  
• Max( )
  
• Min( ) 
• Min( )
• Avg( )
  

we will use the following employees table for our example

 

COUNT( )

Write SQL query to retrieve the total number of employees.

 

SELECT COUNT(*) AS count_employees FROM employees;

 

 

Write SQL query to retrieve the number of employees in department number 3.

 

SELECT COUNT(*) AS no_of_emp FROM employees WHERE dept_id=3

 

Note: count(*) will retrieve all values including NULL values from the specified column

SUM( )

Write a query to retrieve the sum of salary column

 

select sum(salary) as sum_of_salary from employees;

 

 MAX( )

Write a query to retrieve the max salary from employees table.

 

SELECT MAX(salary) as max_of_salary FROM EMPLOYEES;

 

 MIN( )

Write a query to retrieve the minimum salary from employees table.

 

SELECT MIN(salary) as min_of_salary FROM employees;

 

AVG( )

Write a query to retrieve the average salary from employees table.

 

SELECT AVG(salary) as avg_of_salary FROM employees;