SQL - COUNT(), SUM() & AVG() Functions

The SQL COUNT() function is used to return the number of rows satisfies the specified condition.

The SQL SUM() function is used to return the sum of a numeric column which satisfies the given criteria.

The SQL AVG() function is used to return the average value of a numeric column which satisfies the given criteria.

Syntax

The syntax for using COUNT(), SUM() and AVG() functions are given below:

/* SQL COUNT() Function */
SELECT COUNT(column_name) 
FROM table_name
WHERE condition(s);

/* SQL SUM() Function */
SELECT SUM(column_name) 
FROM table_name
WHERE condition(s);

/* SQL AVG() Function */
SELECT AVG(column_name) 
FROM table_name
WHERE condition(s);

Example:

Consider a database table called Employee with the following records:

• To count the number of records in the Employee table where age is greater than 25, the SQL code is:

  SELECT COUNT(Name) AS EmployeeGT25 
  FROM Employee
  WHERE Age > 25;
  

  
  

  This will produce the result as shown below:

  EmployeeGT25
  4

• To find out the total salary paid to all employees with age greater than 25, the SQL code is:

  SELECT SUM(Salary) AS TotalSalary_AgeGT25 
  FROM Employee
  WHERE Age > 25;
  

  
  

  This result of the following code will be:

  TotalSalary_AgeGT25
  11700

• To fetch the average salary of an employee with age greater than 25, the SQL code is:

  SELECT AVG(Salary) AS AvgSalary_AgeGT25
  FROM Employee
  WHERE Age > 25;
  

  
  

  This result of the above code will be:

  AvgSalary_AgeGT25
  2925