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Shuffle problem [message #172196]

Mon, 30 September 2013 07:26

richard

Messages: 213
Registered: June 2013

Karma: 0

Senior Member

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.
I want to extract the first 20 rows from each table.
Then shuffle that and create the list.
Somehting similar to shuffling a deck of cards.

So that my playlist might look like:

1965 #4
1963 #13
1969 #18
1961 #10
1960 #3

What ways can I do this?

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Re: Shuffle problem [message #172199 is a reply to message #172196]

Mon, 30 September 2013 10:18

Denis McMahon
Messages: 634
Registered: September 2010

Karma: 0

Senior Member

On Mon, 30 Sep 2013 03:26:58 -0400, richard wrote:

> ... tables ... rows

This sounds like a database thing. Find an appropriate database group.

> Then shuffle that and create the list.

Have you looked at array functions?

http://www.php.net/manual/en/function.shuffle.php

--
Denis McMahon, denismfmcmahon(at)gmail(dot)com

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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: 0

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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Solved my shuffle problem! [message #182978 is a reply to message #172196]

Mon, 30 September 2013 18:52

richard

Messages: 213
Registered: June 2013

Karma: 0

Senior Member

http://mroldies.net/play200.php

Decided to use an array on the page rather than using the tables.
Each time you refresh the page, you get a different list.

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Re: Shuffle problem [message #182980 is a reply to message #182973]

Mon, 30 September 2013 22:24

Scott Johnson
Messages: 196
Registered: January 2012

Karma: 0

Senior Member

On 9/30/2013 6:48 AM, Erwin Moller wrote:
> 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]
>

Oh Erwin.

Welcome to Richards world of RDB design.

I am no expert but we have all asked the same question and the answers
will make your eyes bleed.

Scotty

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Re: Shuffle problem [message #182999 is a reply to message #172196]

Wed, 02 October 2013 02:02

Lew Pitcher
Messages: 60
Registered: April 2013

Karma: 0

Member

On Monday 30 September 2013 03:26, in comp.lang.php, "richard"
<noreply(at)example(dot)com> 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.
> I want to extract the first 20 rows from each table.
> Then shuffle that and create the list.
> Somehting similar to shuffling a deck of cards.
>
> So that my playlist might look like:
>
> 1965 #4
> 1963 #13
> 1969 #18
> 1961 #10
> 1960 #3
>
> What ways can I do this?

$numbers = range(1, 200);
shuffle($numbers);
foreach ($numbers as $number)
{
$seq = $number % 20;
$year = 1950 + floor($number / 20);
printf("%4u #%d<br/>",$year,$seq);
}

--
Lew Pitcher
"In Skills, We Trust"
PGP public key available upon request

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