PostgreSQL PI() Function

Summary: in this tutorial, you will learn how to use the PostgreSQL PI() function to return the pi value.

Introduction to the PostgreSQL PI() function

In PostgreSQL, the PI() function returns the value of pi denoted by the Greek letter (π), which is approximately equal to 3.14

Here’s the syntax of the PI() function:

PI()

The PI() function takes no arguments and returns the constant value of PI, which is 3.141592653589793.

PostgreSQL PI() function examples

Let’s take some examples of using the PI() function examples.

1) Basic PI() function examples

The following statement uses the PI() function to return the constant PI value:

SELECT PI();

Output:

pi
-------------------
 3.141592653589793

The following example uses the PI() function to calculate the area of a circle with a radius of 10:

SELECT PI() * 10 * 10 area;

Output:

area
-------------------
 314.1592653589793
(1 row)

2) Using the PI() function with table data

First, create a table called circles that stores the radiuses of circles:

CREATE TABLE circles(
   id INT GENERATED ALWAYS AS IDENTITY,
   radius DEC(19,2) NOT NULL,
   PRIMARY KEY(id)
);

Second, insert rows into the circles table:

INSERT INTO circles(radius)
VALUES(10), (20), (25)
RETURNING *;

Output:

id | radius
----+--------
  1 |  10.00
  2 |  20.00
  3 |  25.00
(3 rows)

Third, calculate the areas of circles using the PI() function:

SELECT id, radius, PI() * radius * radius area
FROM circles;

Output:

id | radius |        area
----+--------+--------------------
  1 |  10.00 |  314.1592653589793
  2 |  20.00 | 1256.6370614359173
  3 |  25.00 | 1963.4954084936207
(3 rows)

To make the area more readable, you can use the ROUND() function:

SELECT
  id,
  RADIUS,
  ROUND((PI() * RADIUS * RADIUS)::NUMERIC, 2) AREA
FROM
  circles;

Output:

id | radius |  area
----+--------+---------
  1 |  10.00 |  314.16
  2 |  20.00 | 1256.64
  3 |  25.00 | 1963.50
(3 rows)

Summary

Use the PI() function to return the pi value.