How do I return random numbers as a column in SQL

Question

I'm running a SQL query on SQL Server 2005, and in addition to 2 columns being queried from the database, I'd also like to return 1 column of random numbers along with them. I tried this:

select column1, column2, floor(rand() * 10000) as column3 
from table1

Which kinda works, but the problem is that this query returns the same random number on every row. It's a different number each time you run the query, but it doesn't vary from row to row. How can I do this and get a new random number for each row?

Answer 1

I use c# for dealing with random numbers. It's much cleaner. I have a function I use to return a list of random number and a unique key, then I just join the uniqueKey on the row number. Because I use c#, I can easily specify a range within which the random numbers must fall.

Here are the steps to making the function: http://www.sqlwithcindy.com/2013/04/elegant-random-number-list-in-sql-server.html

Here is what my query ends up looking like:

SELECT 
   rowNumber, 
   name, 
   randomNumber
FROM dbo.tvfRandomNumberList(1,10,100) 
INNER JOIN (select ROW_NUMBER() over (order by int_id) as 'rowNumber', name from client        
            )as clients
ON clients.rowNumber = uniqueKey

Answer 2

Query

select column1, column2, cast(new_id() as varchar(10)) as column3 
from table1

Answer 3

I realize this is an older post... but you don't need a view.

select column1, column2, 
  ABS(CAST(CAST(NEWID() AS VARBINARY) AS int)) % 10000 as column3 
from table1

Answer 4

select RAND(CHECKSUM(NEWID()))

Answer 5

You need to use a UDF

first:

CREATE VIEW vRandNumber
AS
SELECT RAND() as RandNumber

second:

CREATE FUNCTION RandNumber()
RETURNS float
AS
  BEGIN
  RETURN (SELECT RandNumber FROM vRandNumber)
  END

test:

SELECT dbo.RandNumber(), *
FROM <table>

Above borrowed from Jeff's SQL Server Blog

Answer 6

WARNING

Adam's answer involving the view is very inefficient and for very large sets can take out your database for quite a while, I would strongly recommend against using it on a regular basis or in situations where you need to populate large tables in production.

Instead you could use this answer.

Proof:

CREATE VIEW vRandNumber
AS
SELECT RAND() as RandNumber

go 

CREATE FUNCTION RandNumber()
RETURNS float
AS
  BEGIN
  RETURN (SELECT RandNumber FROM vRandNumber)
  END

go 

create table bigtable(i int)

go 

insert into bigtable 
select top 100000 1 from sysobjects  a
join sysobjects b on 1=1

go 

select cast(dbo.RandNumber() * 10000 as integer) as r into #t from bigtable 
-- CPU (1607) READS (204639) DURATION (1551)

go

select ABS(CAST(CAST(NEWID() AS VARBINARY) AS int)) % 10000 as r  into #t1 
from bigtable
-- Runs 15 times faster - CPU (78) READS (809) DURATION (99)

Profiler trace:

alt text http://img519.imageshack.us/img519/8425/destroydbxu9.png

This is proof that stuff is random enough for numbers between 0 to 9999

-- proof that stuff is random enough 
select avg(r) from #t
-- 5004
select STDEV(r) from #t
-- 2895.1999 

select avg(r) from #t1
-- 4992
select STDEV(r) from #t1
-- 2881.44 


select r,count(r) from #t
group by r 
-- 10000 rows returned 

select r,count(r) from #t1
group by r 
-- 10000 row returned