MySQL | primary key needs resetting - php

Question

I have a table which stores the ID of support cases using the primary key (column name = caseid).
I have now got to about 100,000 caseid and the number is just too big. I wish to somehow start from a lower number such as 1000.
How do I achieve something like this by not having to delete/archive existing records and not having to change the unique caseid's to another column (keep it as the primary key column)

Answer 1

To reset Primary Key, you can follow below steps:
Create temporary table with structure same as main table. Let's say table name is tbl_cases
CREATE TABLE tbl_cases_tmp LIKE tbl_cases;
ALTER TABLE tbl_cases_tmp ADD old_caseid int NOT NULL DEFAULT '0';
DUMP all data from tbl_cases to tbl_cases_tmp. caseid will be stored in old_caseid column.
INSERT INTO tbl_cases_tmp (name, summary, old_caseid)
SELECT name, summary, caseid FROM tbl_cases;
For any other tables having references to tbl_cases. Let's say tbl_reference
UPDATE tbl_reference tr
JOIN tbl_cases_tmp tc
ON tr.caseid = tc.old_caseid
SET tr.caseid = tc.caseid;
Before using Steps 4 and 5, ensure your tables tbl_cases_tmp and all references are properly updated.
Drop tbl_cases
DROP table tbl_cases;
Rename tbl_cases_tmp to tbl_cases
RENAME TABLE tbl_cases_tmp TO tbl_cases;

Answer 2

What about find lowest id and subtract its Value from all ids?
Then you'll be able to re-set the id to a lower number
Edit:
This suppose that there are unused ids and no recods related to them

Answer 3

In case your problem is with conveying the caseid e.g. from the customer via phone to the help desk you might consider leaving the actual case id as-is but change the alphabet/set of digits when showing it.
E.g. switch from decimal to hexadecimal and you've increased the range of values that can be displayed as four digits/characters from 9999 to 65535 (hex:ffff).
Now consider a different set of digits like 3479ACEFHJKLMNPRTUVWXY* and the range of numbers that can be displayed using only four digits/characters increases quite a lot.
<?php
echo getCode(234255), "\r\n"; // up until "here": four digits
echo getCode(234256), "\r\n"; // ok, now it's five
echo getCode(5100000), "\r\n"; // but stays five until > 5 millions
function toBase(/* positiv integer*/ $n, array $alphabet) {
$retval = '';
do {
$retval = $alphabet[ $n%count($alphabet) ] . $retval;
$n = intval( $n / count($alphabet) );
}
while( ($n=intval($n)) > 0);
return $retval;
}
function getCode(/*int*/ $caseid) {
static $alphabet = ['3','4','7','9','A','C','E','F','H','J','K','L','M','N','P','R','T','U','V','W','X','Y'];
return toBase($caseid, $alphabet);
}
prints
YYYY
43333
YTYAA
*) an alphabet containing only unambiguous characters.