Rearranging primary keys - php

Question

I have a PHP page which interacts with this small MySQL database table with a simple structure. ID, Name, Address are the fields. ID is the primary key.
+------+------------+-------------+
| ID | Name | Country |
|______|____________|_____________|
| E001 | Stephen | America |
| E002 | John | Britain |
| E003 | Kate | Canada |
| E004 | Carlos | Spain |
| E005 | James | Australia |
|______|____________|_____________|
If I remove the record at E003, it looks like this.
+------+------------+-------------+
| ID | Name | Country |
|______|____________|_____________|
| E001 | Stephen | America |
| E002 | John | Britain |
| E004 | Carlos | Spain |
| E005 | James | Australia |
|______|____________|_____________|
A gap appears between E002 and E004.
Is there a way to fill in that gap? Like this
+------+------------+-------------+
| ID | Name | Country |
|______|____________|_____________|
| E001 | Stephen | America |
| E002 | John | Britain |
| E003 | Carlos | Spain |
| E004 | James | Australia |
|______|____________|_____________|
Earlier record which had E004, fall into the place of E003. Former E005 gets the number E004 and so on. Like the records take a step back.
Is there a way to do this programmatically?

Answer 1

Is there a reason you need to renumber them? The key values shouldn't really matter. If they do (i.e., they are used for outside purposes), consider having the external key be a regular column in the table and let the primary key be an auto-increment integer field. Even if you do this, you still probably shouldn't be renumbering keys. That would mean that all external dependencies would need to be updated as well. There's just not much value in doing it.
But, if you have to...
If the key is auto-increment (which it should be), you can do this:
ALTER TABLE MyTable DROP ID;
ALTER TABLE MyTable ADD COLUMN ID INT NOT NULL PRIMARY KEY AUTO_INCREMENT FIRST;
If it's not, then you can do several things, but the easiest might be to use variables to act as a counter. To make this easier, please don't use a string primary key, but instead use a plain numeric primary key.
SET #id = 0;
UPDATE MyTable
SET ID = (#id := #id + 1)
ORDER BY ID;

Answer 2

In your database table ID is primary key and it is alphanumeric.
I don't think so it is a good way for rearranging primary key in table. All its relation with other table will be messed up.
Try to use numeric primary key instead of string.
If you use numeric primary key, you can rearrange them by dropping and recreating primary key column with auto increment.

Answer 3

Since your ID field is not an integer field you can't do it with just one query and you need to do a loop over all records after the gap and update the ID field.
But a better way might be to change the ID filed type to auto increment unsigned integer and then by knowing the last ID before the gap equals to gID you can do a query like this :
UPDATE table_name SET `ID` = (`ID` - 1) WHERE `ID` > gID;
Then you just need to update your auto_increment value:
ALTER TABLE `table_name` AUTO_INCREMENT = (SELEC `ID` FROM `table_name` ORDER BY `ID` DESC LIMIT 1);
Since all the records in your ID field have the letter 'E' in common, it might be possible to get rid of this letter and change the field type to an AUTO INCREMENT UNSIGNED INTEGER