Inserting rows with missing IDs [General]

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From: "Bob McConnell" on 3 May 2010 09:40

From: Andre Polykanine

> It's not a strictly PHP question, however since I use that with PHP,
> I'm asking it there.
> How can I accomplish the task of inserting rows into MySql database
> with missing IDs? Say, I have rows with IDs 1, 2, 3, 5, 9, 12, 17, and
> 195. How do I make the check that allows to insert firstly the missing
> IDs and only then apply the auto-increment?

Why are they missing? Were they present at one time then deleted? If so,
were they used as foreign keys from another table or referenced in
queries for other data that may still reference those empty rows?

Think about the ramifications of old data in other tables that may be
inherited when new rows are assigned a deleted ID.

Bob McConnell

From: tedd on 3 May 2010 12:11

At 4:34 PM +0300 5/3/10, Andre Polykanine wrote:
>Hello everyone,
>It's not a strictly PHP question, however since I use that with PHP,
>I'm asking it there.
>How can I accomplish the task of inserting rows into MySql database
>with missing IDs? Say, I have rows with IDs 1, 2, 3, 5, 9, 12, 17, and
>195. How do I make the check that allows to insert firstly the missing
>IDs and only then apply the auto-increment?
>Thanks!

Andre:

Why? Why worry about the ID's that are missing?

Does your code depend upon the data being in sequential ID's? If so,
it's probably not a good idea to do that and you should rethink how
you pull your data.

Cheers,

tedd

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From: Richard Quadling on 4 May 2010 11:08

On 3 May 2010 14:34, Andre Polykanine <andre(a)oire.org> wrote:
> Hello everyone,
> It's not a strictly PHP question, however since I use that with PHP,
> I'm asking it there.
> How can I accomplish the task of inserting rows into MySql database
> with missing IDs? Say, I have rows with IDs 1, 2, 3, 5, 9, 12, 17, and
> 195. How do I make the check that allows to insert firstly the missing
> IDs and only then apply the auto-increment?
> Thanks!

Using PHP, you could find the missing IDs by using the following steps.

1 - Get the current maximum ID.

SELECT max(ID) as Max FROM table

If you aren't interested in the ones before the first valid ID then
also retrieve the min(ID).

So you end up with $MinID = 1, $MaxID = 195.

2 - Get all the current IDs.

SELECT ID FROM table

So you end up with $KnownIDs = array(1,2,3,5,9,12,17,195);

3 - Use the range() function in PHP to build an array from the lowest
id (or 1) to the highest id.

$RangeIDs = range($MinID, $MaxID);

4 - Use array_diff($RangeIDs, $KnownIDs); to find the missing IDs.

So ...

<?php
$MinID = 1;
$MaxID = 30; // Edited to suit output
$KnownIDs = array(1,2,3,5,9,12,17,30); // Edited to suit output
$RangeIDs = range($MinID, $MaxID);
print_r(array_diff($RangeIDs, $KnownIDs));
?>

outputs ...

Array
(
[3] => 4
[5] => 6
[6] => 7
[7] => 8
[9] => 10
[10] => 11
[12] => 13
[13] => 14
[14] => 15
[15] => 16
[17] => 18
[18] => 19
[19] => 20
[20] => 21
[21] => 22
[22] => 23
[23] => 24
[24] => 25
[25] => 26
[26] => 27
[27] => 28
[28] => 29
)

--
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Richard Quadling
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From: Richard Quadling on 4 May 2010 11:13

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