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Generating Randomly Ordered SQL Server Result Sets

This article describes a straightforward method of generating randomly sorted result sets in SQL Server. This procedure has a number of potential uses, such as displaying a few randomly chosen news article headlines on a website, or it could be used to randomly select a few advertisements while ensuring the same advert isn't always displayed at the top of the advertising space.

Although it is possible to introduce randomness in SQL Server using time functions, in practice this does not work (especially in stored procedures) because of the speed of execution of the SQL statements [hence many or all of the rows could be returned in exactly the same instant of time]. A far better alternative is, therefore, to use the NewID function to create a unique identifier for each row returned. This returns GUID-like identifiers such as AF53DB47-766F-44B7-82EC-7459E353B3F3.The results set can then be ordered by this column.

The use of the NewID function is shown in this example stored procedure shown below:

CREATE PROCEDURE sp_GetAdverts
(
@MaxNumberOfAdverts int
)
AS

set rowcount @MaxNumberOfAdverts

select top 100 t_Adverts.AdvertID,
    t_Adverts.TargetURL,
    t_Adverts.AltTag,

    newID() as 'RandomColumn'

from t_Adverts
where getdate() between t_Adverts.AdvertStartDate and t_Adverts.AdvertEndDate

order by newID()
GO

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