PostgreSQL SETSEED() Function

The PostgreSQL SETSEED() function is used to set the seed for the subsequent RANDOM() function calls. The value of seed must be between -1.0 and 1.0, inclusive.

The RANDOM() function returns a random number between 0 (inclusive) and 1 (exclusive). It returns a completely random number if no seed is provided. Otherwise, it returns a repeatable sequence of random numbers, if seed is provided.

Syntax

SETSEED(seed)

Parameters

Return Value

Nothing is returned.

Example:

The example below shows the usage of SETSEED() function.

/* no seed value is provided,
  hence the result can vary */
SELECT RANDOM();
Result: 0.6763981107454846

/* seed value is provided using SETSEED(0.5) */
SELECT SETSEED(0.5);
SELECT RANDOM();
Result: 0.2499104186659835

/* seed value is provided using SETSEED(0.3) */
SELECT SETSEED(0.3), RANDOM();
Result: 0.5499641674664169

Random Number in a given Range

The PostgreSQL RANDOM() function can be used to create a random number between a given range. For example - to create a random number in a range [a, b), the following formula can be used:

SELECT RANDOM()*(b-a) + a;

Example:

In the example below, the RANDOM function is used to create a random number between a range [100, 200).

/* no seed value is provided,
  hence the result can vary */
SELECT RANDOM()*(200-100) + 100;
Result: 143.67012152790102

/* seed value is provided using SETSEED(0.5) */
SELECT SETSEED(0.5);
SELECT RANDOM()*(200-100) + 100;
Result: 124.99104186659835

/* seed value is provided using SETSEED(0.5) */
SELECT SETSEED(0.3);
SELECT RANDOM()*(200-100) + 100;
Result: 154.99641674664167

Random Integer in a given Range

The PostgreSQL RANDOM() function can be used to create a random integer between a given range. For example - to create a random integer in a range [a, b), the following formula can be used:

SELECT FLOOR(RANDOM()*(b-a)) + a;

Example:

In the example below, the RANDOM function is used to create a random integer between a range [500, 600).

/* no seed value is provided,
  hence the result can vary */
SELECT FLOOR(RANDOM()*(600-500)) + 500;
Result: 533

/* seed value is provided using SETSEED(0.5) */
SELECT SETSEED(0.5);
SELECT FLOOR(RANDOM()*(600-500)) + 500;
Result: 524

/* seed value is provided using SETSEED(0.3) */
SELECT SETSEED(0.3);
SELECT FLOOR(RANDOM()*(600-500)) + 500;
Result: 554