Select based on record number in result set

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Select based on record number in result set

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thangavelu_arun@yahoo.com
Starting Member

8 Posts

Posted - 2011-09-01 : 12:03:28

Hi,

Thanks for you input.

Lets assume that i have a temp table with 5000 rows, i have to select 100 rows as sample based on the following formula.

x + (i * y) where i goes from 1 to 99

For example, x = 25, y = 50, i from 1 to 99 and first row selected is row number 25. Here x and y are generated based on the random number and total number of rows taken for selection.

1st row selected - Row number 25 (assume)
2nd row selected - x + (i * y) = 25 + (1 * 50) = 75 Row number
3rd row selected - x + (i * y) = 25 + (2 * 50) = 125 Row number
4th row selected - x + (i * y) = 25 + (3 * 50) = 175 Row number
................
100th row selected - x + (i * y) = 25 + (99 * 50) = 4975 Row number

Is there anyway to include this in a select statement like using mod function?

select * from @table where id = ....

Thanks,
Velu

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2011-09-02 : 00:31:34

will you be inputting x and y random values or are they also to be generated as part of the logic?

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

thangavelu_arun@yahoo.com
Starting Member

8 Posts

Posted - 2011-09-02 : 08:07:54

They are generated in the logic using random number and number of records in the temp table.
X = total number of records / 100
Y = random number * X

Thanks,
Velu

Transact Charlie
Master Smack Fu Yak Hacker

3451 Posts

Posted - 2011-09-02 : 09:19:58

Can you not get away with just selecting a completely random sample?


SELECT TOP 100 *
FROM tbSample
ORDER BY NEWID()

It would be easier. Otherwise you are going to have to give each row a row number based on some sort of ordering.

Charlie
===============================================================
Msg 3903, Level 16, State 1, Line 1736
The ROLLBACK TRANSACTION request has no corresponding BEGIN TRANSACTION

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