UNIFORM

Description

Using the given random seed, uniformly sample and generate random numbers within a specific range.

Syntax

UNIFORM( <min> , <max> , <gen> )

Parameters

Parameter	Description
<min>	The lower limit of the random number, accepts numeric type, must be a literal
<max>	The upper limit of the random number, accepts numeric type, must be a literal
<gen>	Integer, random seed, commonly generated by the RANDOM function randomly.

Return value

Return a random number within [<min>, <max>]. If both <min> and <max> are integers, the return value type is BIGINT, otherwise it is DOUBLE.

Note that unlike Snowflake's common usage, because the RANDOM function in Doris returns a floating-point number between 0 and 1 by default, if you use RANDOM() as a random seed, you should attach a multiplier to make the result distributed within an integer range. See the examples for details.

Example

When all input parameters are integers, return an integer:

select uniform(-100, 100, random() * 10000) as result from numbers("number" = "10");

+--------+
| result |
+--------+
|    -82 |
|    -79 |
|     21 |
|     19 |
|     50 |
|     53 |
|   -100 |
|    -67 |
|     46 |
|     40 |
+--------+

When input parameters are not all integers, return the double type:

select uniform(1, 100., random() * 10000) as result from numbers("number" = "10");

+-------------------+
| result            |
+-------------------+
| 84.25057360297031 |
| 63.34296160793329 |
|  81.8770598286311 |
| 26.53334147605743 |
| 17.42787914185705 |
| 2.532901549399078 |
| 63.72223367924216 |
| 78.42165786093118 |
|   18.913688179943 |
| 41.73057334477316 |
+-------------------+

Must be literal parameters:

select uniform(1, unix_timestamp(), random() * 10000) as result from numbers("number" = "10");

ERROR 1105 (HY000): errCode = 2, detailMessage = The second parameter (max) of uniform function must be literal

Must be literal parameters:

select uniform(1, ksint, random()) from fn_test;

ERROR 1105 (HY000): errCode = 2, detailMessage = The second parameter (max) of uniform function must be literal

Fixed seeds will produce fixed results (the result of random() is distributed between 0 and 1, and when used directly, the seed parameter of uniform is always 0):

select uniform(-100, 100, random()) as result from numbers("number" = "10");

+--------+
| result |
+--------+
|    -68 |
|    -68 |
|    -68 |
|    -68 |
|    -68 |
|    -68 |
|    -68 |
|    -68 |
|    -68 |
|    -68 |
+--------+

When any input is NULL, the output is also NULL：

select uniform(-100, NULL, random() * 10000) as result from numbers("number" = "10");

+--------+
| result |
+--------+
|   NULL |
|   NULL |
|   NULL |
|   NULL |
|   NULL |
|   NULL |
|   NULL |
|   NULL |
|   NULL |
|   NULL |
+--------+

select k0, uniform(0, 1000, k0) from it order by k0;

+------+----------------------+
| k0   | uniform(0, 1000, k0) |
+------+----------------------+
| NULL |                 NULL |
|    1 |                  134 |
|    2 |                  904 |
|    3 |                  559 |
|    4 |                  786 |
|    5 |                  673 |
+------+----------------------+