MariaDB/MySQL - How to query JSON based on key of nested object - mysql

Question

Given the following JSON object stored in MariaDB/MySQL:
SET #j = '{
"thing": {
"sub_things": [
{
"attribute": [
{ "1": 40 },
{ "5": 25 },
{ "13": 35 }
]
},
{
"attribute": [
{ "2": 50 },
{ "7": 50 }
]
}
]
}
}'
How would I query this to return sub_things where one of the objects in the attribute array has a particular key e.g. where the key is 13 this should return the first sub_thing.
Thanks!

Answer 1

I'm not sure if in a single query you can achieve what you need.
The following stored procedure, perhaps, can give you some ideas (stored procedure works for MariaDB and for MySQL):
> DROP PROCEDURE IF EXISTS `JSON_query_based_on_key`;
Query OK, 0 rows affected (0.01 sec)
> DELIMITER //
> CREATE PROCEDURE `JSON_query_based_on_key`(
-> `json` TEXT,
-> `key` VARCHAR(5)
-> )
-> BEGIN
-> DECLARE `sub_things_current` INT
-> DEFAULT JSON_LENGTH(`json`, '$.thing.sub_things') - 1;
->
-> WHILE (`sub_things_current` > -1) DO
-> IF NOT JSON_CONTAINS_PATH(
-> `json`,
-> 'one',
-> CONCAT('$.thing.sub_things[', `sub_things_current`, '].attribute[*]."', `key`, '"')
-> ) THEN
-> SET `json` := JSON_REMOVE(
-> `json`,
-> CONCAT('$.thing.sub_things[', `sub_things_current`, ']'));
-> END IF;
-> SET `sub_things_current` := `sub_things_current` - 1;
-> END WHILE;
->
-> SELECT JSON_EXTRACT(`json`, '$.thing');
-> END//
Query OK, 0 rows affected (0.00 sec)
> DELIMITER ;
> CALL `JSON_query_based_on_key`('{
'> "thing": {
'> "sub_things": [
'> {
'> "attribute": [
'> { "1": 40 },
'> { "5": 25 },
'> { "13": 35 }
'> ]
'> },
'> {
'> "attribute": [
'> { "2": 50 },
'> { "7": 50 }
'> ]
'> }
'> ]
'> }
'> }', '13');
+---------------------------------------------------------------------+
| JSON_EXTRACT(`json`, '$.thing') |
+---------------------------------------------------------------------+
| {"sub_things": [{"attribute": [{"1": 40}, {"5": 25}, {"13": 35}]}]} |
+---------------------------------------------------------------------+
1 row in set (0.00 sec)
Query OK, 0 rows affected (0.00 sec)
Modify the code as you need it.
See db<>fiddle for MariaDB (10.2.6) and db-fiddle for MySQL (5.7.17).