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Re: Shuffle problem [message #182973 is a reply to message #172196]

Mon, 30 September 2013 13:48

Erwin Moller
Messages: 228
Registered: September 2010

Karma:

Senior Member

On 9/30/2013 9:26 AM, richard wrote:
> On my site I want to create a play list that is randomly selected when the
> page is loaded.
> I have ten tables, each with 100 rows.

[sidestepping]
That strikes me as pretty strange database design.
Why do you have 10 tables if they contain the same things?
In case each table represents a year, you might want to add a
year-column to the table, and fill that with the right value.
That way you'll have one clear table.
[end sidestepping]

> I want to extract the first 20 rows from each table.

Ask yourself: What are the FIRST 10 rows?
What "first 10" means depends on your ORDER BY clause.

In general: getting the first 10 is done in a database specific manner.
For example SQL Server:
SELECT TOP 10 FROM sometablename;

In Postgres you'll use: LIMIT and OFFSET

etc.

Look it up for your database.

> Then shuffle that and create the list.
> Somehting similar to shuffling a deck of cards.

Solution: Do 10 selects, each returning 10 rows.
Store them in an array.
OR
Create one query using UNION to glue them together.

Then shuffle it in some way, for example with the shuffle function.

Good luck,
Erwin Moller

>
> So that my playlist might look like:
>
> 1965 #4
> 1963 #13
> 1969 #18
> 1961 #10
> 1960 #3
>
> What ways can I do this?
>

--
"That which can be asserted without evidence, can be dismissed without
evidence."
-- Christopher Hitchens

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[Message index]

		Shuffle problem By: richard on Mon, 30 September 2013 07:26
		Re: Shuffle problem By: Denis McMahon on Mon, 30 September 2013 10:18
		Re: Shuffle problem By: Erwin Moller on Mon, 30 September 2013 13:48
		Re: Shuffle problem By: Scott Johnson on Mon, 30 September 2013 22:24
		Solved my shuffle problem! By: richard on Mon, 30 September 2013 18:52
		Re: Shuffle problem By: Lew Pitcher on Wed, 02 October 2013 02:02

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