Do i really need an auto increment id column? - mysql

Question

I have a table structure with META_ID | KEY | VALUE | USER_ID where META_ID is auto-increment. Now in my php logic
1 get the result key-value pairs per user
2 delete the key value row per user
3 update or insert the key value pair for a already known USER_ID
4 insert key value pair for a new user
But the META_ID keeps growing, so i was wondering if i could just delete the META_ID column?
Case logic
An registered user or returning registered user can update their form over time if they haven't submit it yet. So overtime an user can select and deselect certain form options and update, insert or delete is triggered.
Now the logic behind "returning user deselects a key (and the row needs to be deleted)" gives me a problem. That's why i just delete all users key-value pairs. But what would be the right way?
So if the key-value exists in the db table but not in $params i need to delete it!
btw here's my function
function user_shopping_meta_data($params) {
global $wpdb;
$shopping_meta_table = 'wp_shopping_metavalues';
$wp_user_id = $params['wp_user_id'];
//1 CHECK IF USER HAS KEY VALUE PAIRS
$checkKeyValues = $wpdb->get_results("SELECT meta_shopping_key FROM $shopping_meta_table WHERE wp_user_id = '$wp_user_id'");
//2 WE DELETE
$qdel = $wpdb->delete($shopping_meta_table, array('wp_user_id' => $wp_user_id));
//3 UPDATE OR INSERT
foreach ($params as $key => $val) {
//variables
if (is_array($val)) {
$val = json_encode($val);
}
$shopping_meta_values = array(
'wp_user_id' => $wp_user_id,
'meta_shopping_key' => $key,
'meta_shopping_value' => $val
);
if (count($checkKeyValues) > 0) {//3 USER IS KNOWN SO UPDATE and/or INSERT new key-value
foreach ($checkKeyValues as $check) {
//UPDATE OR INSERT
if (($key != "wp_user_id")) {
//FOR UPDATE where
$shopping_meta_where = array('meta_shopping_key' => $key, 'wp_user_id' => $wp_user_id);
$result = $wpdb->get_results("SELECT * FROM $shopping_meta_table WHERE meta_shopping_key = '" . $key . "' AND wp_user_id = '$wp_user_id'");
if (count($result) > 0) {//KEY ALREADY EXISTS FOR USER
$return .= $wpdb->update($shopping_meta_table, array('meta_shopping_key' => $key, 'meta_shopping_value' => $val), $shopping_meta_where) . '<br/>';
//$return .= 'UDPATE<br/>';
} else {//KEY IS NEW
$return .= $wpdb->insert($shopping_meta_table, $shopping_meta_values) . '<br/>';
// $return .= 'INSERT for old';
}
}//.end $key
}//.end foreach checkKeyValue
}//.end count
else {//4 INSERT KEY VALUE PAIR FOR NEW USER
if (($key != "wp_user_id")) {
$return .= $wpdb->insert($shopping_meta_table, $shopping_meta_values) . '<br/>';
// $return .= 'INSERT NEW';
}
}
}//.end each
echo 'Test return: ' . $return;
}

Answer 1

You won't gain much by deleting it. You might think that you save some space, but in fact you don't. An auto_increment column is always also (part of) the primary key. If you delete it, MySQL will create an "implicit" primary key, which is not visible but necessary for MySQL to identify rows. Also you will lose some comfort like not being able to use LAST_INSERT_ID().

Answer 2

You can very well delete it. It is just a unique ID. If you can distinguish different rows without the META_ID or you do not need to distinguish rows, then META_ID is redundant.

Answer 3

If i can give you a suggest is better to leave that field as a history.
If you need to want to know what is the last action done for that user you can order by META_ID.
Is usefull to have a primary key in a table. But this is just a suggest

Answer 4

I suggest you have a primary key that you are sure of that it is unique. It is a good idea to use a auto-increment column for this because you will always be sure that it is unique.