Aggregate Functions:

Oracle has many built-in functions which are used to process numbers or strings. They are very useful as we can directly use them , we just have to write the aggregate function name and in braces the column name on which we have to perform any calculations.

1. COUNT() function:

COUNT function is applied to those situation when we have to count the number of tuples(rows) in a table.

Example of COUNT function:

SELECT COUNT(Name) FROM Employee WHERE City = 'Dehradun';

The above query will count the number of names who belongs to city Dehradun.

2. MAX() Function:

It selects the maximum value from a column like if we need to find highest salary we can use MAX() function.

Example of MAX function:

SELECT MAX(AGE) FROM Employee; 

The above query will fetch highest age from employee table.

3. MIN() Function:

It selects the minimum value from a column like if we need to find lowest salary we can use MIN() function.

Example of MIN function:

SELECT MIN(AGE) FROM Employee; 

The above query will fetch smallest age from employee table.

4. AVG() Function:

It calculates the average value for a column on which it is applied.

SELECT AVG(Salary) FROM Employee;

The above query will fetch the average of Salary column.

5. SUM() Function:

It calculates the sum of all values for a column on which it is applied.

SELECT SUM(Salary) FROM Employee;

The above query will fetch the total sum of Salary column.