How to remove specific numbers from list MySQL - php

Question

I have a comma separated list of numbers in a MySQL entry 'id_user' like so:
127,130,150,12,4,7,8,9
What is the best way to find a number in this comma-separated list and (1) remove it with the comma if it's with other numbers or (2) just remove itself if the number is by itself like:
127
Then update the MySQL entry.
So if I wanted to remove 150 from the list, it would be updated in the MySQL as:
127,130,12,4,7,8,9
I want to avoid trying to remove the id '12' but end up removing the '12's in numbers like 127 or 512
Thank you!

Answer 1

Reading between the lines, it sounds to me like you are storing a list of foreign keys in a comma-separated string field to represent a many-to-many relationship. This is not a good idea.
What you should do instead is create a table to store the relations.
For example, lets say you have a table called users and you want to store friend relationships between them. What you are doing is something like this (N.B. I realised this is actually not a great example as I wrote the end but I'm sticking with it for now):
id | name | friends
------+--------+-----------
1 | Dave | 2,4
2 | Bob | 1
3 | Tom | 4
4 | Bill | 1,3
Whereas what it's much better to do is something like this:
users
id | name
------+--------
1 | Dave
2 | Bob
3 | Tom
4 | Bill
friends
id | user | friend
------+--------+----------
1 | 1 | 2
2 | 1 | 4
3 | 2 | 1
4 | 3 | 4
5 | 4 | 1
6 | 4 | 3
To select Dave's friends you can do
SELECT u.*
FROM friends f
JOIN users u ON u.id = f.friend
WHERE f.user = 1
...and to delete the relationship between Dave and Bob (what you want to do here), you can simply do
DELETE FROM friends
WHERE (
user = 1 AND friend = 2
) OR (
user = 2 AND friend = 1
)

Answer 2

Using PHP:
$array = explode(',', $string);
$pos = array_search('127', $array);
unset($array[$pos]);
$string = implode(',', $array);
Or using MySQL:
REPLACE(column, '127,', '')
REGEX_REPLACE(column, '127$', '')
Get UDF REGEX_REPLACE - https://launchpad.net/mysql-udf-regexp with ^127$

Answer 3

In PHP:
$string="," . $string . ",";
str_replace("127,", "", $string);
Or you could split the string:
$list=explode(",",$string);
$new="";
foreach($list as $item){
if($item!="127"){
$new.=$item.",";
}
$new=substr_replace($new ,"",-1);
That should work.

Answer 4

As pyrate suggests try this in MySQL
TRIM(BOTH ',' FROM REGEX_REPLACE(column, '127\,?', ''))
using the UDF
Hope this helps