RE: quick mysql question

From: Alex Hall <mehgcap@xxxxxxx>
To: programmingblind@xxxxxxxxxxxxx
Date: Wed, 08 Apr 2009 11:00:10 -0400

Okay. One lastthing: the skip is always from the start of thematched rows, right?


Have a great day,
Alex

----- Original Message -----
From: "Holdsworth, Lynn" <Lynn.Holdsworth@xxxxxxxxxxx
To: <programmingblind@xxxxxxxxxxxxx
Date sent: Wed, 8 Apr 2009 15:41:48 +0100
Subject: RE: quick mysql question

Hi Alex,

Apologies, I've probably confused things.

Limit 2, 7 would skip two rows and bring back the 3rd to the 9th

row.

Cheers, Lynn

-----Original Message-----
From: programmingblind-bounce@xxxxxxxxxxxxx
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Alex

Hall

Sent: 08 April 2009 15:41
To: programmingblind@xxxxxxxxxxxxx
Subject: RE: quick mysql question

So limit 2,7 would be records 2-8, or 3-9? If the index starts at

0 then

it should start at the number you skipped, right?

Have a great day,
Alex

----- Original Message -----
From: "Holdsworth, Lynn" <Lynn.Holdsworth@xxxxxxxxxxx
To: <programmingblind@xxxxxxxxxxxxx
Date sent: Wed, 8 Apr 2009 15:09:59 +0100
Subject: RE: quick mysql question

Hi Alex,

Remember that the skip argument has a zero index, so Niran's

example

would actually skip 10 records and bring back from the 11th row

onwards.

Cheers, Lynn

-----Original Message-----
From: programmingblind-bounce@xxxxxxxxxxxxx
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of niran
Sent: 09 April 2009 03:10
To: programmingblind@xxxxxxxxxxxxx
Subject: Re: quick mysql question

The syntax of limit clause is
select ....  limit skip , size
The limit clause will skip specified number of rows from the

result and

return the rows specified in size.  For example select * from

users limit

10 , 10; will return 10 users starting from 10th user in the

result set.

Alex Hall wrote:

That makes a lot of sense.  I have heard of limit 20, which will
select the first 20 rows, but what is the comma? I guess I

should say:

what is the syntax of the limit clause? Thanks!

Have a great day,
Alex

----- Original Message -----
From: "Holdsworth, Lynn" <Lynn.Holdsworth@xxxxxxxxxxx
To: <programmingblind@xxxxxxxxxxxxx
Date sent: Wed, 8 Apr 2009 13:04:14 +0100
Subject: RE: quick mysql question

Hi Alex,

I don't think you need row numbers to accomplish paging.

I've written some PHP code below, which you'll need to tweak a

bit.

If you can put the page number in the querystring:-

http://www.something.com/somepage.php?page=3

Then you can tweak the SQL statement with a limit clause:-

<?php
....
Extract($_GET); //exposes variables from the querystring
$recordsPerPage = 5; //Number of records on each page

//If page number not set, then set it to 1 If (!$page) { $page =

1; }

//Calculate the first record you want to retrieve on this page
//Index is zero-based $firstRecord = $recordsPerPage *

($page-1);

//Now build the SQL query with the limit clause $query = "select
<fieldNames From <tableName Where <whereClause Limit

$firstRecord,

$recordsPerPage"; ....
?

Let us know if this works for you.

Cheers, Lynn

Lynn Holdsworth
Web Analyst/Programmer - www.rnib.org.uk

-----Original Message-----
From: programmingblind-bounce@xxxxxxxxxxxxx
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Alex

Hall

Sent: 08 April 2009 12:47
To: programmingblind@xxxxxxxxxxxxx
Subject: Re: quick mysql question

Okay.  How would I use this to control which records are

displayed? Say

I have records 1-8, and the php page displays the first two,

then

the

next two, and so on, moving to the next two every time a "next"

button

is clicked.  How would the page know which two (or however many

it was

set to display per page) to get? What if the user wants to go

back? Does

this make sense?
Sorry if this comes out looking strange, I think my bn's ueb

translator

is going crazy.

Have a great day,
Alex

----- Original Message -----
From: "Octavian Rasnita" <orasnita@xxxxxxxxx
To: <programmingblind@xxxxxxxxxxxxx
Date sent: Wed, 8 Apr 2009 08:28:16 +0300
Subject: Re: quick mysql question

The indexes in a table are used for creating relations with the

records from

other tables, and it would be a total mess if those indexes

would

change.

If you need to find how many records there are in a table, you

can simply

count them using:

select count(*) from table_name;

Or you can put some conditions like:

select count(*) from table_name where column1=123 and

another_column="abc"

and another_one like '%bla%';

--
Octavian

----- Original Message -----
From: "Alex Hall" <mehgcap@xxxxxxx
To: <programmingblind@xxxxxxxxxxxxx
Sent: Wednesday, April 08, 2009 6:21 AM
Subject: Re: quick mysql question

Okay, so the numbering is lost if you delete.  Is there a more

robust way

of numbering, so that you would have gotten:
1, abc'
2, 'ghi'
3, 'kno'
instead? I need the index of each record to always be sequential

so that I

can know how many total records there are and also know which

ones I have

used in the displaying of all of them.

Have a great day,
Alex

----- Original Message -----
From: "R.  Haynie" <rhaynie@xxxxxxxxxxx
To: programmingblind@xxxxxxxxxxxxx Date sent: Tue, 07 Apr 2009
22:51:24 -0400
Subject: Re: quick mysql question

An example is worth a thousand words...

create table tbl1 (fld1 INTEGER AUTO_INCREMENT,
fld2 char(3),
PRIMARY KEY  (fld1));

insert into tbl1 (fld2) values ('abc'), ('def'), ('ghi'),

('jkl');

select * from tbl1;
-- gives you:
1, 'abc'
2, 'def'
3, 'ghi'
4, 'jkl'

delete from tbl1 where fld1 in (2, 4); insert into tbl1 (fld2)
values ('mno'); select * from tbl1;
-- gives you:
1, 'abc'
3, 'ghi'
5, 'mno'

HTH.
-Rodney

Alex Hall wrote:

Hi all,
If I have a table of records and one column is an autoincrement,

what

happens when I delete a record? I want to use the autoincrement

as an

index, so records 1, 2, 3, and 4 exist where 1-4 are the indexes

of

the records, If you delete record 3, do you then have records 1,

2,

and 3, or 1, 2, and 4? If it is the second case, is there a

better way

to have an index of each record? I need to know how many

recordsI am

using on a page (it is sort of a photo viewer so I need to know

which

pictures are being shown and how many more there are) and how

many

total there are to go.  Thanks.

Have a great day,
Alex
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