Earlier I blogged about creating random numbers using tsql functions.  Here are two techniques for selecting a random value from a pre-defined range of values in a tsql script.  The first technique uses a table variable ( MSSQL 2000 + ), and the second uses a Common Table Expression or CTE ( MSSQL 2005+ ).

Select a random value using a table variable

-- var to hold random integer
declare @field_val int

-- create table var to hold value range [ 0, 512, 1024, 2048, 4096 ]
-- inserting the first value sets the structure for the table variable
SELECT 0 AS 'num'
INTO #temp

-- insert data into table var
INSERT INTO #temp VALUES ( 512 )
INSERT INTO #temp VALUES ( 1024 )
INSERT INTO #temp VALUES ( 2048 )
INSERT INTO #temp VALUES ( 4096 )

-- assign random value
SELECT TOP 1 @field_val = num FROM #temp ORDER BY NEWID()

-- show value
SELECT @field_val

-- drop the table variable
DROP TABLE #temp

Select a random value using a CTE

-- define our data table
WITH data( car )
AS
(
	-- UNION together our range of values
	SELECT 'audi' AS 'car'
	UNION
	SELECT 'bmw' AS 'car'
	UNION
	SELECT 'infinity' AS 'car'
	UNION
	SELECT 'lexus' AS 'car'
	UNION
	SELECT 'porsche' AS 'car'
)
-- select a random value
SELECT TOP 1 car FROM data
ORDER BY NEWID()

Both of these techniques can be used with numbers or text. Just be sure to mind your quotes, and variable datatypes.  Being able to pick a random value in data generation scripts has proven very useful.  I hope this helps somebody else out as well.

Tags: #table, cte, howto, mssql, mssql2000, mssql2005, random, table variable, tsql

This entry was posted on Saturday, January 2nd, 2010 at 6:08 pm and is filed under database, development, microsoft, random, tips and tricks, tsql. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.