In PostgreSQL, mod() is a mathematical function that returns the remainder from division of the first argument (the dividend) by the second argument (the divisor).

Syntax

The syntax goes like this:

mod(y, x)

The function returns the remainder of y/x.

Example

Here’s an example to demonstrate how it works.

SELECT mod(5, 2);

Result:

1

In this case, 5 divided by 2 has a quotient of 2 and a remainder of 1, so the result is 1.

Negative Arguments

Here’s an example with negative arguments.

SELECT 
  mod(-5, 2),
  mod(5, -2),
  mod(-5, -2);

Result:

 mod | mod | mod
-----+-----+-----
  -1 |   1 |  -1

Zero Dividend

Here’s an example with a dividend of zero.

SELECT mod(0, 2);

Result:

0

Division by Zero

Now let’s swap it around and make the divisor zero.

SELECT mod(2, 0);

Result:

ERROR: division by zero