SQL AGGREGATE FUNCTIONS – AVG

SQL AGGREGATE FUNCTIONS – AVG

SQL has 5 different aggregate functions (MIN, MAX, COUNT, SUM & AVG). Here we will be looking at the AVG function. The AVG function returns the average of all the values of a column in the table. 

SYNTAX – 

SELECT AVG(column1) FROM table_name WHERE condition;

Usually, the aggregate functions are used in conjunction with the GROUP BY/ HAVING clause, which gives even more meaningful results. The syntax for the query using AVG function using GROUP BY / HAVING clause is mentioned below –

SELECT column1, AVG(column2) FROM table_name WHERE condition1 GROUP BY column1 HAVING condition2;

 

At first, these might look little complicated, but once we go over few examples, it will make more sense. 



Illustration – Consider the below employee table in the database which stores the information pertaining to employees in ABC company –

 

IDemployee_nameagesalaryDepartmentmanager_name
1Jimmy3280000SalesVijay
2James3585000SalesVijay
3Helen3382000HRKrish
4Mary2678000QualityWarner
5William3390000HRKrish
6Vijay38105000SalesRoger
7Krish38105000HRRoger

Query 1 – What is the average salary of all the employees of ABC company?

  SELECT AVG(salary) FROM employee;

AVG(salary)

————— 

89285.71428571429

Query 2 – What is the average salary of all employees of ABC company who belongs to sales department?

  SELECT AVG(salary) FROM employee WHERE department=’sales’;

AVG(salary)

————— 

90000

Query 3 – What is the average salary of employees in ABC company by each department.

  SELECT Department, AVG(salary) FROM employee GROUP BY Department;

DepartmentAVG(salary)
Sales90000
HR92333.33333
Quality78000

 

Query 4 – What is the list of departments at ABC company, which has more than average employee salary less than or equal to 90000 in their department?

  SELECT Department, AVG(salary) FROM employee GROUP BY Department HAVING AVG(salary) <= 90000;

DepartmentAVG(salary)
Sales90000
Quality78000

 

 

 

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