Re: quick mysql question

  • From: "Octavian Rasnita" <orasnita@xxxxxxxxx>
  • To: <programmingblind@xxxxxxxxxxxxx>
  • Date: Wed, 8 Apr 2009 08:28:16 +0300

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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