PI() function in MySQL

PI() function in MySQL is used to return the Pi value. The default number of decimal places displayed is seven, but MySQL uses the full double-precision value internally. Syntax :

PI()

Parameter : This method does not accept any parameter. Returns : It returns the Pi value i.e. 3.141593. Example-1 : Returning the default value of Pi using PI Function.

SELECT PI() AS DefaultPiValue;

Output :

DefaultPiValue
3.141593

Example-2 :

Returning the value of Pi up to 18 decimal places using PI Function .  

SELECT PI()+0.000000000000000000 
AS PiValue;

Output :

PiValue
3.141592653589793000

Example-3 : Using PI Function to calculate the area and perimeter of all circles in a column. To demonstrate, let us create a table named Circle.

CREATE TABLE Circle(
Circle_id INT AUTO_INCREMENT,  
Radius DECIMAL(10, 3) NOT NULL,
PRIMARY KEY(Circle_id )
);

Now, insert some data to the Circle table.

INSERT INTO Circle(Radius )
VALUES
(2 ),(3),(10 ),(12.5 ),(6.80),
(4.60 ),(6),(20),(25) ;

So, the Circle Table is as follows.

SELECT * FROM Circle;

Circle_id	Radius
1	2.000
2	3.000
3	10.000
4	12.500
5	6.800
6	4.600
7	6.000
8	20.000
9	25.000

Now, we will calculate the area and perimeter of every circle using PI function.

SELECT Circle_id, Radius,
PI() * Radius * Radius  AS Area,
2 * PI() * Radius AS Perimeter
FROM Circle;

Output :

Circle_id	Radius	Area	Perimeter
1	2.000	12.566371	12.566371
2	3.000	28.274334	18.849556
3	10.000	314.159265	62.831853
4	12.500	490.873852	78.539816
5	6.800	145.267244	42.725660
6	4.600	66.476101	28.902652
7	6.000	113.097336	37.699112
8	20.000	1256.637061	125.663706
9	25.000	1963.495408	157.079633