Seeding a Random Integer
Jim_Knicely
- Select Field - Administrator
The RANDOM function returns a uniformly-distributed random number x, where 0 <= x < 1 and the RANDOMINT functions returns one of the n integers from 0 through n – 1.
In yesterday’s tip we learned that we can use the SEEDED_RANDOM function to re-use generated numbers. There is not a SEEDED_RANDOMINT function, but that’s not a problem. Create your own!
Example:
dbadmin=> SELECT random() random1, random() random2, random() random3;
random1 | random2 | random3
-------------------+-------------------+-------------------
0.206615947652608 | 0.308142327470705 | 0.124399376800284
(1 row)
dbadmin=> SELECT seeded_random(1) random1, seeded_random(1) random1,
dbadmin-> seeded_random(2) random2, seeded_random(2) random2;
random1 | random1 | random2 | random2
-------------------+-------------------+------------------+------------------
0.417021998437122 | 0.417021998437122 | 0.43599490262568 | 0.43599490262568
(1 row)
dbadmin=> CREATE OR REPLACE FUNCTION seeded_randomint (x INT, y INT) RETURN INT
dbadmin-> AS
dbadmin-> BEGIN
dbadmin-> RETURN FLOOR(SEEDED_RANDOM(x)*(y));
dbadmin-> END;
CREATE FUNCTION
dbadmin=> SELECT seeded_randomint(1, 100) random1, seeded_randomint(1, 100) random1,
dbadmin-> seeded_randomint(2, 100) random2, seeded_randomint(2, 100) random2;
random1 | random1 | random2 | random2
---------+---------+---------+---------
41 | 41 | 43 | 43
(1 row)
Helpful Links:
https://www.vertica.com/docs/9.2.x/HTML/Content/Authoring/SQLReferenceManual/Functions/Mathematical/RANDOM.htm
Have fun!
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