The RADIANS() function in SQLite is a mathematical function that converts an angle from degrees to radians. This can be handy when working with trigonometric calculations in your database queries, as some mathematical functions (such as SIN(), TAN()) expect angles in radians rather than degrees.

Syntax

RADIANS(angle_in_degrees)

Where angle_in_degrees is a numeric expression representing an angle in degrees that you want to convert to radians.

How It Works

The function uses the mathematical formula:

radians = degrees × (π/180)

Example 1

Here’s a simple example to demonstrate:

SELECT radians(23);

Output:

+-------------------+
|    radians(23)    |
+-------------------+
| 0.401425727958696 |
+-------------------+

This is the equivalent of doing the following:

SELECT 23 * pi() / 180;

Output:

+-------------------+
|  23 * pi() / 180  |
+-------------------+
| 0.401425727958696 |
+-------------------+

Using the RADIANS() function helps our code to be more concise.

Example 2

Let’s say you’re working with a table of angles and need to convert them to radians for further calculations:

-- Create a sample table
CREATE TABLE angles (
    angle_id INTEGER PRIMARY KEY,
    angle_degrees FLOAT
);

-- Insert some sample data
INSERT INTO angles (angle_degrees) VALUES 
    (0),
    (45),
    (90),
    (180),
    (360);

-- Convert angles to radians
SELECT 
    angle_degrees,
    RADIANS(angle_degrees) as angle_radians
FROM angles;

Output:

+---------------+-------------------+
| angle_degrees |   angle_radians   |
+---------------+-------------------+
| 0.0           | 0.0               |
| 45.0          | 0.785398163397448 |
| 90.0          | 1.5707963267949   |
| 180.0         | 3.14159265358979  |
| 360.0         | 6.28318530717959  |
+---------------+-------------------+

Rounding the Results

We can use the ROUND() function to round the results if required:

SELECT 
    angle_degrees,
    ROUND(RADIANS(angle_degrees), 2) as angle_radians
FROM angles;

Output:

+---------------+---------------+
| angle_degrees | angle_radians |
+---------------+---------------+
| 0.0           | 0.0           |
| 45.0          | 0.79          |
| 90.0          | 1.57          |
| 180.0         | 3.14          |
| 360.0         | 6.28          |
+---------------+---------------+

Passing the Wrong Argument Type

Passing an argument of the wrong type results in NULL:

SELECT radians('ten');

Output:

+----------------+
| radians('ten') |
+----------------+
| null           |
+----------------+