RANDOM

Declaration

RANDOM(seed)

Description

The function generates a 64-bit integer pseudo-random value.

• seed is an integer. Different seed values generate different random number sequences.
• RANDOM() uses the MT19937 pseudo-random number generation algorithm, which has a very large random space. It will generate 2¹⁹⁹³⁷ - 1 random elements before repeating the same sequence.

Examples

The following example shows how to use RANDOM() to generate random numbers.

SELECT RANDOM(4) FROM TABLE(GENERATOR(3));
+---------------------+
| RANDOM(4)           |
+---------------------+
| 5267436225003336391 |
| -851690886662571060 |
| 1738617244330437274 |
+---------------------+
3 rows in set (0.001 sec)

The following example shows how to use the result of RANDOM() as a random input for a distribution function.

SELECT UNIFORM(1, 100, RANDOM()) FROM TABLE(GENERATOR(4));
+---------------------------+
| UNIFORM(1, 100, RANDOM()) |
+---------------------------+
|                        66 |
|                        71 |
|                        52 |
|                        14 |
+---------------------------+
4 rows in set (0.001 sec)

The following example shows a special scenario where, when the parameter of RANDOM() is a variable, the seed is recalculated each time.

SELECT * FROM t1;
+------+
| c1   |
+------+
|    3 |
|    4 |
|    5 |
|    1 |
|    1 |
+------+
5 rows in set

SELECT t1.c1, RAND(t1.c1), RANDOM(t1.c1) FROM TABLE(GENERATOR(1)), t1;
+------+---------------------+----------------------+
| c1   | RAND(t1.c1)         | RANDOM(t1.c1)        |
+------+---------------------+----------------------+
|    3 |  0.9057697559760601 |  1084041170817055659 |
|    4 | 0.15595286540310166 |  5267436225003336391 |
|    5 | 0.40613597483014313 |  3192483991702052534 |
|    1 | 0.40540353712197724 | -6753783847308464280 |
|    1 | 0.40540353712197724 | -6753783847308464280 |
+------+---------------------+----------------------+
5 rows in set (0.001 sec)