In MySQL, the PI() function returns the value of π (pi). The number π is a mathematical constant approximately equal to 3.14159 (although it can also be displayed with much greater precision than this).

The PI() function displays π with a default precision of 7 (i.e. 3.141593), however MySQL uses the full double-precision value internally.

Syntax

The syntax goes like this:

PI()

So this function doesn’t require (or accept) any arguments.

Example 1 – Default Display

Here’s a basic example to demonstrate what PI() returns.

SELECT PI();

Result:

+----------+
| PI()     |
+----------+
| 3.141593 |
+----------+

In this case π is returned with a default precision of 7.

Example 2 – Increased Precision

Here’s an example of displaying π using greater precision.

SELECT PI()+0.000000000000000000;

Result:

+---------------------------+
| PI()+0.000000000000000000 |
+---------------------------+
|      3.141592653589793000 |
+---------------------------+

Example 3 – Reduced Precision

Here’s an example of displaying π using reduced precision. In this case we use the ROUND() function to specify how many decimal places to return.

SELECT ROUND(PI(), 2);

Result:

+----------------+
| ROUND(PI(), 2) |
+----------------+
|           3.14 |
+----------------+

And if we round it to 4 decimal places the digit 5 will be rounded up to 6.

SELECT ROUND(PI(), 4);

Result:

+----------------+
| ROUND(PI(), 4) |
+----------------+
|         3.1416 |
+----------------+