The PI() function in SQLite returns the mathematical constant π (pi), which is approximately 3.14159265358979. It is used to represent the ratio of the circumference of a circle to its diameter.

The PI() function is commonly employed in mathematical computations, particularly in geometry, trigonometry, and other scientific calculations involving circles and angles.

Syntax

The syntax for the PI() function is straightforward:

PI()

This function does not take any arguments and returns the constant value of π.

Example 1

Here’s what happens when we call PI() by itself:

SELECT PI();

Output:

+------------------+
|       PI()       |
+------------------+
| 3.14159265358979 |
+------------------+

It simply returns the mathematical constant π.

Example 2: Using PI() to calculate the circumference of a circle

The formula for the circumference of a circle is:

C = 2πr

where C is the circumference and r is the radius.

Here’s an example that uses PI() in such a calculation:

SELECT 2 * PI() * 5 AS Circumference;

In this example, we are calculating the circumference of a circle with a radius of 5 units.

Result:

+------------------+
|  Circumference   |
+------------------+
| 31.4159265358979 |
+------------------+

Example 3: Using PI() with ROUND() to round the result

The ROUND() function rounds a numeric value to a specified number of decimal places. For example, to round the result of the circumference calculation to 2 decimal places:

SELECT ROUND(2 * PI() * 5, 2) AS RoundedCircumference;

In this case, we are rounding the result of the circumference calculation to 2 decimal places.

Result:

+----------------------+
| RoundedCircumference |
+----------------------+
| 31.42                |
+----------------------+

Contexts for Using PI()

The PI() function can be used in various contexts, including:

• Geometric Calculations: When calculating areas and circumferences of circles, spheres, or other geometric shapes.
• Trigonometric Functions: Pi is a fundamental constant in trigonometry, as angles in trigonometric functions like sin(), cos(), and tan() are often measured in radians, where 360° = 2π radians.
• Scientific and Engineering Calculations: Pi is frequently used in physics and engineering for calculations involving periodic phenomena, waveforms, or rotational motion.
• Data Analysis and Modeling: In statistical models, physics simulations, or machine learning algorithms, the constant π is often used in various formulas.

In general, the PI() function can be used wherever the value of π is needed in mathematical expressions or formulas that involve circular or rotational measurements.