MySQL REPLACE() in a set - mysql

Question

So I have a table of banners, and in that table there is a field that tells me on which sites they should be shown, like a poor man's relational table.
Banner.jpg | ABC,CDE,FGH
Banner2.jpg | IPO,IPOMON,IPOHLM
And so on. And I use find_in_set() to collect banners for a specific site.
Now, I want to write a script that replaces these values, say "ABC" should be "XZY". So I run this:
update banners set sites = replace(sites, 'ABC', 'XZY')
And it's a done deal. But, problem arises if I want to change "IPO" to "APO" for instance, since this query:
update banners set sites = replace(sites, 'IPO', 'APO')
Would result in this data:
Banner.jpg | XYZ,CDE,FGH
Banner2.jpg | APO,APOMON,APOHLM
Which is undesirable. So how do I change just "IPO" and not "IPOMON" when doing a replace() or similar function? I would want a "replace_in_set()" function so to speak.
Any ideas?

Answer 1

You can use a query like this. first it adds a ',' at the begin and the end of the set. Then you can change your set and TRIM remove the ','.
UPDATE banners
SET sites = TRIM(BOTH ',' FROM REPLACE( CONCAT(',',sites,','), ',IPO,', ',APO,') );

Answer 2

I don't think there is a nice/pretty way to do this. In order to have IPO as a singular and IPO as part of a list changed you'd have to do something like this.
UPDATE banners SET
sites = REPLACE(sites,
IF(sites LIKE '%IPO,%', 'IPO,', 'IPO'),
IF(sites LIKE '%IPO,%', 'APO,', 'APO')
);
The more things to catch the more complex the IFs have to be but you get the idea.

Answer 3

DO the fact you ha a string the you could use 'IPO,'
update banners set sites = replace(sites, 'IPO,', 'APO,')

Answer 4

You should have the tables normalized so that you can use an UPDATE on the field in which value equals your desired replacement. Take a look at this example:
/* create the banner data table and add banner.jpg and banner2.jpg */
CREATE TABLE banner
(`banner_id` int, `description` varchar(11))
;
INSERT INTO banner
(`banner_id`, `description`)
VALUES
(1, 'banner.jpg'),
(2, 'banner2.jpg')
;
/* create the website data table and:
ABC, CDE, FGH, IPO, IPOMON, and IPOHLM */
CREATE TABLE website
(`site_id` int, `banner_id` int, `site` varchar(6))
;
INSERT INTO website
(`site_id`, `banner_id`, `site`)
VALUES
(1, 1, 'ABC'),
(2, 1, 'CDE'),
(3, 1, 'FGH'),
(4, 2, 'IPO'),
(5, 2, 'IPOMON'),
(6, 2, 'IPOHLM')
;
/* update the website data table to change IPO to APO */
UPDATE `website`
SET `site` = "APO"
WHERE `site` = "IPO";
SELECT * FROM `website`
Fiddle: Live Demo

Answer 5

I gave a +1 to Bernd Buffin's answer, because it at least accomplishes the substitution without fetching the data into an application to split and rejoin the string.
The following doesn't answer your question, but I thought I'd post it here to benefit other readers in the future.
I tried to test the new REGEXP_REPLACE() function in MySQL 8.0.4, because I thought the following would work, but it doesn't:
mysql> SELECT REGEXP_REPLACE('IPO,IPOMON,IPOHLM', '[[:<:]]IPO[[:>:]]', 'APO');
ERROR 3686 (HY000): Illegal argument to a regular expression.
MySQL changed their regexp library in 8.0.4 and the new library doesn't support the [[:<:]] [[:>:]] word-boundary patterns.