Database Auto Count what about delete?

[Sims]

Hi,

I have a table that give a unique ID to certain Articles.
To give the ID i simply use the Auto count of the DB.

But what happens when i delete a record? i am now missing an ID.
How can i insert a row and give it the first available number?

For example ID 1, 2, 4, 5, 6

i would Insert and set the ID number to 3.

Regards
Sims

[Andy Hassall]

On Sun, 22 Feb 2004 16:19:37 +0200, "Sims" <si*********@hotmail.com> wrote:

I have a table that give a unique ID to certain Articles.
To give the ID i simply use the Auto count of the DB.

But what happens when i delete a record? i am now missing an ID.
How can i insert a row and give it the first available number?

For example ID 1, 2, 4, 5, 6

i would Insert and set the ID number to 3.

Don't read any meaning into an auto-generated ID, treat it as a meaningless
but (a) unique and (b) not used before label for the row. If it reused values,
then point (b) would be violated, and when you start using transactions, trying
to fill gaps would cause further severe problems (some of which are the exact
same problems ones auto generated IDs are there to work around).

What reason do you have for wanting to fill 'gaps'?

--
Andy Hassall <an**@andyh.co.uk> / Space: disk usage analysis tool
<http://www.andyh.co.uk> / <http://www.andyhsoftware.co.uk/space>

[Thierry B.]

Hi,

auto-increment fields (Mysql) or Sequence objects in many other databases
are automatically incremented (default is +1 but can be changed) to give you
an unique identifier. You SHOULD NEVER try to alter these sequences and fill
the gaps, this is the way it works!

--
Thierry Bothorel
<?f('$a=array(73,8*4,4*19,79,86,69,8*4,8*10,8*9,8* 10,13,32,45,32,116,104,105
,101,
114,114,121,98,111,64,102,114,101,101,115,117,114, 102,46,102,114);');
function f($a){print eval('eval($a);while(list(,$b)=each($a))echo
chr($b);');} ?> (Tobias Schlitt)

"Sims" <si*********@hotmail.com> a écrit dans le message de news:
c1*************@ID-162430.news.uni-berlin.de...

Hi,

I have a table that give a unique ID to certain Articles.
To give the ID i simply use the Auto count of the DB.

But what happens when i delete a record? i am now missing an ID.
How can i insert a row and give it the first available number?

For example ID 1, 2, 4, 5, 6

i would Insert and set the ID number to 3.

Regards
Sims

[Sims]

I have a table that give a unique ID to certain Articles.
To give the ID i simply use the Auto count of the DB.

But what happens when i delete a record? i am now missing an ID.
How can i insert a row and give it the first available number?

For example ID 1, 2, 4, 5, 6

i would Insert and set the ID number to 3.
Don't read any meaning into an auto-generated ID, treat it as a

meaningless but (a) unique and (b) not used before label for the row. If it reused values, then point (b) would be violated, and when you start using transactions, trying to fill gaps would cause further severe problems (some of which are the exact same problems ones auto generated IDs are there to work around).

What reason do you have for wanting to fill 'gaps'?

Well, the user can create articles and assign different values to help sort
the article.

For example

Article = "Some article".
Type = 7

where the types are

"HR Dpt" = 0x01;
"Account"= 0x02;
"Management" = 0x04... and so on.

So every 'type' is stored in the database, but the administrator can
add/edit/delete types.

I know i could/should not replace old styles but rather creates new ones but
there comes a time when the user can purge the database and remove old items
and re-use deleted styles.

Sims

[Mike Discenza]

Sims wrote:

>I have a table that give a unique ID to certain Articles.
>To give the ID i simply use the Auto count of the DB.
>
>But what happens when i delete a record? i am now missing an ID.
>How can i insert a row and give it the first available number?
>
>For example ID 1, 2, 4, 5, 6
>
>i would Insert and set the ID number to 3.

Don't read any meaning into an auto-generated ID, treat it as a

meaningless

but (a) unique and (b) not used before label for the row. If it reused

values,

then point (b) would be violated, and when you start using transactions,

trying

to fill gaps would cause further severe problems (some of which are the

exact

same problems ones auto generated IDs are there to work around).

What reason do you have for wanting to fill 'gaps'?

Well, the user can create articles and assign different values to help
sort the article.

For example

Article = "Some article".
Type = 7

where the types are

"HR Dpt" = 0x01;
"Account"= 0x02;
"Management" = 0x04... and so on.

So every 'type' is stored in the database, but the administrator can
add/edit/delete types.

I know i could/should not replace old styles but rather creates new ones
but there comes a time when the user can purge the database and remove old
items and re-use deleted styles.

Sims

I don't think MySQL does this, but there is a thing known as 'referential
integrity'. I think that is what you are looking for.

But, you can code something like this in PHP. If someone tries to delete
the Type, have it check to make sure there isn't something that uses that
Type. If there is error out with a message telling the person to move
those articles to a new Type then try again.