AGGREGATE FUNCTIONS

SQL GROUP Functions

Group functions are built-in SQL functions that operate on groups of rows and return one value for the entire group. These functions are: COUNT, MAX, MIN, AVG, SUM, DISTINCT

SQL COUNT (): This function returns the number of rows in the table that satisfies the condition specified in the WHERE condition. If the WHERE condition is not specified, then the query returns the total number of rows in the table.

For Example: If you want the number of employees in a particular department, the query would be:

SELECT COUNT (*) FROM employee 
WHERE dept = 'Electronics'; 

The output would be '2' rows.

If you want the total number of employees in all the department, the query would take the form:

SELECT COUNT (*) FROM employee;

The output would be '5' rows.

SQL DISTINCT(): This function is used to select the distinct rows.

For Example: If you want to select all distinct department names from employee table, the query would be:

SELECT DISTINCT dept FROM employee;

To get the count of employees with unique name, the query would be:

SELECT COUNT (DISTINCT name) FROM employee;

SQL MAX(): This function is used to get the maximum value from a column.

To get the maximum salary drawn by an employee, the query would be:

SELECT MAX (salary) FROM employee;

SQL MIN(): This function is used to get the minimum value from a column.

To get the minimum salary drawn by an employee, he query would be:

SELECT MIN (salary) FROM employee;

SQL AVG(): This function is used to get the average value of a numeric column.

To get the average salary, the query would be

SELECT AVG (salary) FROM employee;

SQL SUM(): This function is used to get the sum of a numeric column

To get the total salary given out to the employees,

SELECT SUM (salary) FROM employee;