MySQL JSON extract a single value by id - mysql

Question

I have a database with a JSON array in column extra_fields. I need to extract one value by id.
The JSONs looks something like this, though the number of objects is random for each row:
[
{"id":"1","value":"48768"},
{"id":"2","value" ["String","http:someurl"]},
{"id":"5","value":"somevalue"},
{"id":"6","value":""},
{"id":"8","value":"Op-Ed"},
{"id":"9","value":"8111,13498,15408"},
{"id":"10","value":"30"},
{"id":"11","value":"This is the target string"}
]
I can extract an array of ids with:
SELECT extra_fields->>"$[*].id" FROM esqt7_k2_items;
I can extract an array of values with:
SELECT extra_fields->>"$[*].value" FROM esqt7_k2_items;
I can extract a single value at the nth zero-ordered object position with:
SELECT extra_fields->>"$[2].value" FROM esqt7_k2_items;
But the problem is that there's a variable number of objects and I specifically need the value of object id = 11. JSON_EXTRACT doesn't seem to support filtering, as every variation of a JSONPATH seems to fail. $..[?(#.id=11)].value works as a JSONPATH, but this (and many variants) fails:
SELECT extra_fields->"$.[?(#.id=11)].value" FROM esqt7_k2_items; #FAILS
This is a migration project and the JSON stuff is just how Joomla chose to implement their extra fields. Kind of a pain if you ask me.

Answer 1

One option you can consider (be careful about performance issues):
mysql> SELECT VERSION();
+-----------+
| VERSION() |
+-----------+
| 5.7.19 |
+-----------+
1 row in set (0.00 sec)
mysql> DROP TABLE IF EXISTS `esqt7_k2_items`;
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE IF NOT EXISTS `esqt7_k2_items` (
-> `id` BIGINT UNSIGNED NOT NULL AUTO_INCREMENT PRIMARY KEY,
-> `extra_fields` JSON NOT NULL
-> );
Query OK, 0 rows affected (0.00 sec)
mysql> INSERT INTO `esqt7_k2_items`
-> (`extra_fields`)
-> VALUES
-> ('
'> [
'> {"id": "1", "value": "48768"},
'> {"id": "2", "value": ["String","http:someurl"]},
'> {"id": "5", "value": "somevalue"},
'> {"id": "6", "value": ""},
'> {"id": "8", "value": "Op-Ed"},
'> {"id": "9", "value": "8111,13498,15408"},
'> {"id": "10", "value": "30"},
'> {"id": "11", "value": "This is the target string"}
'> ]
'> '),
-> ('
'> [
'> {"id": "1", "value": ""},
'> {"id": "9", "value": "ONE This is the target string"}
'> ]
'> '),
-> ('
'> [
'> {"id": "6", "value": ""},
'> {"id": "11", "value": "TWO This is the target string"}
'> ]
'> ');
Query OK, 3 rows affected (0.00 sec)
Records: 3 Duplicates: 0 Warnings: 0
mysql> SET #`search_id` := '11';
Query OK, 0 rows affected (0.00 sec)
mysql> SELECT `der`.`id`, `der`.`value`
-> FROM (
-> SELECT
-> `id`,
-> JSON_UNQUOTE(
-> JSON_EXTRACT(`extra_fields`,
-> CONCAT((SELECT
-> JSON_UNQUOTE(
-> JSON_SEARCH(`extra_fields` ->> '$[*].id', 'one', #`search_id`)
-> )
-> FROM `esqt7_k2_items` `esqt7_k2_items_in`
-> WHERE `esqt7_k2_items_out`.`id` = `esqt7_k2_items_in`.`id`
-> ), ".value"
-> )
-> )
-> ) `value`
-> FROM `esqt7_k2_items` `esqt7_k2_items_out`
-> ) `der`
-> WHERE `der`.`value` IS NOT NULL;
+----+-------------------------------+
| id | value |
+----+-------------------------------+
| 1 | This is the target string |
| 3 | TWO This is the target string |
+----+-------------------------------+
2 rows in set (0.00 sec)
See db-fiddle.

Answer 2

Simpliest way i found to get
the value of object id = 11
its by finding the right "index" of the needed object, doing a bit of PHP.
Firstly we get all objects Ids, by your simple request:
> SELECT extra_fields->>"$[*].id" FROM esqt7_k2_items;
then in PHP
$rightIndex = array_search($ids, '11');
and then you get the right object by passing this $rightIndex :
SELECT extra_fields->>"$[$rightIndex].value" FROM esqt7_k2_items;
Simple as hell! The same thing you can do anywhere else, for example, when you need to UPDATE an object in array, or its value/values, etc..
That is, Cheers!