August 7, 2023
Summary: This tutorial shows you how to develop a user-defined function that generates a random number between two numbers.
PostgreSQL provides the random() function that returns a random number between 0 and 1. The following statement returns a random number between 0 and 1.
SELECT random();
random
-------------------
0.867320362944156
(1 row)
To generate a random number between 1 and 11, you use the following statement:
SELECT random() * 10 + 1 AS RAND_1_11;
rand_1_11
------------------
7.75778411421925
(1 row)
If you want to generate the random number as an integer, you apply the floor() function to the expression as follows:
SELECT floor(random() * 10 + 1)::int;
floor
-------
9
(1 row)
Generally, to generate a random number between two integers l and h, you use the following statement:
SELECT floor(random() * (h-l+1) + l)::int;
You can develop a user-defined function that returns a random number between two numbers l and h:
CREATE OR REPLACE FUNCTION random_between(low INT ,high INT)
RETURNS INT AS
$$
BEGIN
RETURN floor(random()* (high-low + 1) + low);
END;
$$ language 'plpgsql' STRICT;
The following statement calls the random_between() function and returns a random number between 1 and 100:
SELECT random_between(1,100);
random_between
----------------
81
(1 row)
If you want to get multiple random numbers between two integers, you use the following statement:
SELECT random_between(1,100)
FROM generate_series(1,5);
random_between
----------------
37
82
19
92
43
(5 rows)
In this tutorial, you have learned how to generate a random number between a range of two numbers.