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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:

EmpIDNameCityAgeSalary
1JohnLondon253000
2MarryNew York242750
3JoParis272800
4KimAmsterdam303100
5RameshNew Delhi283000
6HuangBeijing282800

  • 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