PostgreSQL 18 reference · Math Functions

PostgreSQL GCD() Function

Return the greatest common divisor of two integers, the largest number that divides both. lcm() gives the least common multiple.

PostgreSQL 18 Since 13

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Syntax

gcd(a, b)  |  lcm(a, b)

Parameter	Description
`a, b`	Integers or numerics.

A number of the input type.

GCD and LCM

SELECT gcd(12, 18) AS gcd, lcm(4, 6) AS lcm;

Output

 gcd | lcm
-----+-----
   6 |  12
(1 row)

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Simplify a fraction

SELECT 12 / gcd(12, 18) || '/' || 18 / gcd(12, 18) AS simplified;

Output

 simplified
------------
 2/3
(1 row)

Run this on your computer — see “Get Started” for setup.

Version	Change
PostgreSQL 13	Added

MOD() · Return the remainder of dividing one number by another; x % y does the same. The sign follows the dividend.
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