Oracle COUNT() Function

The Oracle (PL/SQL) COUNT() function returns the count of an expression.

Syntax

The syntax for using COUNT() function is given below:

SELECT COUNT(column_name) 
FROM table_name
WHERE condition(s);

The Oracle (PL/SQL) GROUP BY clause is used to arrange result table into identical groups when one or more columns are used. Please note that it is must to include those column names in a GROUP BY clause which are not encapsulated within the COUNT() function. See the syntax below:

SELECT column1, column2, ...
       COUNT(column_name) 
FROM table_name
WHERE condition(s)
GROUP BY column1, column2, ...;

Parameters

Return Value

Returns the count of non-null value of a given expression.

Example - With Single Column

Consider a database table called Employee with the following records:

To get the count of employees whose age is greater than 25, the following query can be used:

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

This will produce the result as shown below:

Example - Using DISTINCT

The DISTICT clause can be used with COUNT() function. For example - To get the count of distinct (unique) age of the employees, the following code can be used:

SELECT COUNT(DISTINCT Age) AS DistinctAge 
FROM Employee;

This will produce the result as shown below:

Example - Using GROUP BY

To get the count of employees group by their age, the following query can be used:

SELECT Age, COUNT(Age) AS NumberOfEmployee 
FROM Employee
GROUP BY Age;

This result of the above code will be: