Random Number Generator
There are many methods to generate random number in SQL Server.
Method 1 : Generate Random Numbers (Int) between Rang
---- Create the variables for the random number generation DECLARE @Random INT; DECLARE @Upper INT; DECLARE @Lower INT---- This will create a random number between 1 and 999 SET @Lower = 1 ---- The lowest random number SET @Upper = 999 ---- The highest random number SELECT @Random = ROUND(((@Upper - @Lower -1) * RAND() + @Lower), 0) SELECT @Random
Method 2 : Generate Random Float Numbers
SELECT RAND( (DATEPART(mm, GETDATE()) * 100000 )
+ (DATEPART(ss, GETDATE()) * 1000 )
+ DATEPART(ms, GETDATE()) )
Method 3 : Random Numbers Quick Scripts
---- random float from 0 up to 20 - [0, 20)
SELECT 20*RAND()
-- random float from 10 up to 30 - [10, 30)
SELECT 10 + (30-10)*RAND()
--random integer BETWEEN 0
AND 20 - [0, 20]
SELECT CONVERT(INT, (20+1)*RAND())
----random integer BETWEEN 10
AND 30 - [10, 30]
SELECT 10 + CONVERT(INT, (30-10+1)*RAND())Method 4 : Random Numbers (Float, Int) Tables Based with Time
DECLARE @t TABLE( randnum float )
DECLARE @cnt INT; SET @cnt = 0
WHILE @cnt <=10000
BEGIN
SET @cnt = @cnt + 1
INSERT INTO @t
SELECT RAND( (DATEPART(mm, GETDATE()) * 100000 )
+ (DATEPART(ss, GETDATE()) * 1000 )
+ DATEPART(ms, GETDATE()) )
END
SELECT randnum, COUNT(*)
FROM @t
GROUP BY randnum
Method 5 : Random number on a per row basis
---- The distribution is pretty good however there are the occasional peaks.
---- If you want to change the range of values just change the 1000 to the maximum value you want.
---- Use this as the source of a report server report and chart the results to see the distribution
SELECT randomNumber, COUNT(1) countOfRandomNumber
FROM (
SELECT ABS(CAST(NEWID() AS binary(6)) %1000) + 1 randomNumber
FROM sysobjects) sample
GROUP BY randomNumber
ORDER BY randomNumber
Reference : Pinal Dave (http://www.SQLAuthority.com)
pinaldave
Good info, it helped me understand sql rand function better.
However I don’t seem to find an answer to what I’m trying to do.
I have a table that looks like this
Var Number
ff 0
zap 0
zf 0
and so on…
What I want to do is assign a random int positive number for each Number between a certain range.
Is that possible?
Thanks
Hi!
Do you know how to create a random
XX-###
XX are character rand()
### number [0 to 9] rand()
I need to produce or generate at least the first 100 to 1000 count() and more later
thanks
Vince
Hi,
If I need to check the possibilities of numbers generated within given range. if I wanna generate alphanumeric 4 charater values like A2B8,A3A2,..etc. How I find out the number of possibilities
Thanks,
Damith
Great article. I am a noob to sql and know it works but not quite sure. In regards to this bit.
– This will create a random number between 1000 and 9999
SET @Lower = 1000 — The lowest random number
SET @Upper = 9999 — The highest random number
SELECT @Random = Round(((@Upper - @Lower -1) * Rand() + @Lower), 0)
SELECT @Random
I am having a hard time understanding how this works. If I replace the upper with 9999 and the lower with 1000 I get (8998) * Rand() + 1000), 0
This is the section I am not understanding how it would generate a 4 digit random number.
Hi,
I want to select top random generated 3 records from top 30 records order by some column name with out using temporary table or variable.Is it possible?
Thanks in advance.
Teena
Hi Teena,
Try this
SELECT TOP 3 * FROM employees ORDER BY 1
In the random number generator between the range the higher end number, 999. Will never be generated. I tried this by lowering the scope to 1 as low 3 as hi and never got 3 i would get lots of 1’s and 2’s but no 3. So if you want to get the top number you need to add 1 to it to include it within the range.
Hi Pinal,
I am working as a MSSQL as well as aOracle DBA. I have been looking for health check scripts on SQL Server for quite some time. Please advice where I can get good health check scripts
You are the good!!
I would like to find very least missed number from the table. I have a empID field in Employee table. The data would be like this..
empId
0
3
5
6
From above data, the least missed number is: 1
So my query should return a value : 1
How to do this.
Hope you understand my question..
Further to Michael’s comments, also be careful when using method 1 if you require equal probability, as for ranges with a difference of 3 or more the first and last numbers in the range are only c. half as likely to be generated as the ‘middle’ numbers, e.g. a sample of 10000 nos from 1 to 9 (ie @lower=1, @upper = 10):
val: Occurrence (sample):
1 610
2 1296
3 1299
4 1275
5 1244
6 1225
7 1212
8 1235
9 604
It can be difficult to get a random integer within a specified range, with a good quality probability distribution.
The following gives a pretty good distribution, plus is flexible when it comes to specifying the range.
DECLARE @Rand SMALLINT
DECLARE @UpperLimit SMALLINT
DECLARE @LowerLimit SMALLINT
SET @UpperLimit = 1
SET @LowerLimit = -1
SET @Rand =
@LowerLimit+
ABS((CAST(NEWID() AS VARBINARY))%
(1+@UpperLimit-@LowerLimit))
SELECT @Rand
Both the upper and lower limit values are returned. Negative ranges can be specified, but the @UpperLimit must always be greater than the @LowerLimit.
It can easily be made into a UDF or SP.
Please send me some script to t
hi there…. thanks for the sharing, anyway I have this problem regarding to my objective in simulation (markov chain monte carlo). because it seems that every time I “run” the query, the random number seems to be differ than the latest one. Its giving me a hard time in analyzing the system that I simulate.
Is there any possibility to randomize fixed number…..
for example….
1st run (range 1′ cut - 9′ cut)
5*,6,7,8,3,4,2,5,6
2nd run (range 1′ cut - 9′ cut)
5*,6,7,8,3,4,2,5,6
3rd run (range 2′ cut - 10′ cut)
6*,7,8,3,4,2,5,6,8*
please reply as soon as possible.
thanks for your information and sharing.
To Sundar; a quick, dirty way of doing what you want would be something like…
SELECT MIN(empID) + 1 AS lowestMissedValue
FROM Employee
WHERE ((SELECT TOP 1 (empID + 2)
FROM Employee E
WHERE E.empID = Employee.empID) Employee.empID))
It’ll only find values that are missing above the minimum, though, so if your lowest value is 2000, then the first value it could return is 2001.
Damn, it cut out part of the SQL. Basically, you’re retrieving the minimum value plus one, for values where the same minimum value plus TWO is less than or equal to the next highest value, meaning that there’s a gap of at least two numbers between that value and the one following it. You should be able to fill in the SQL gaps from that.
Thank you for your great articule!
Hi, I have a data table , in which i want only selected (4) records when i press next button the next set of selected (4) records should be displayed like paging option in grid view .. is there any query to perform this operation.. so that loading the entire table in to grid can be avoided… please give your comments… thanks in advance
I have a stored procedure that selects a number of rows dependant on various input values -
for example, say the query selects 12 different rows, how can I then rendomly select one of the twelve and drop the other 11?
thankyou
Matt