Complex regex in mysql json - mysql

Question

I have sort of cache column in mysql table column. Lets call it cacheCol It is structured as json.
cacheCol example
{
"23": {
"variationOption": "23",
"productCode": "322992-015",
"price": "150",
"qnt": ""
},
"25": {
"variationOption": "25",
"productCode": "322992-015",
"price": "150",
"qnt": "0"
},
"26": {
"variationOption": "26",
"productCode": "322992-015",
"price": "150",
"qnt": "7"
}
}
I want to select myslq row if specific json part qnt is > 0. In this example part with key 26 is only one to match.
I have worked out regex to check those values:
https://www.regextester.com/?fam=109762
But when i run my query
SELECT * FROM "tbl" WHERE ("cacheCol" REGEXP ('(?<=\"26":\{)[^\{]*"qnt":"[1-9]\d*"(?=.*\})'))
Error shows up:
Got error 'repetition-operator operand invalid' from regexp
Here is sqlfiddle to play around: http://www.sqlfiddle.com/#!9/30335a/1
(Updated sqlfiddle to cover more variations in DB)
Is there any way to work around my regex to be compatible with mysql.
Found some info about mysql 5.7 having json data type maybe where is way to get my desired result avoiding regex?

Answer 1

For Schema like this :
CREATE TABLE IF NOT EXISTS `tbl` (
`id` int(6) unsigned NOT NULL,
`cacheCol` TEXT NOT NULL,
PRIMARY KEY (`id`)
) DEFAULT CHARSET=utf8;
INSERT INTO `tbl` (`id`, `cacheCol`) VALUES
('1', '{"23":{"variationOption":"23","productCode":"322992-015","price":"150","qnt":""}}'),
('2', '{"25":{"variationOption":"25","productCode":"322992-015","price":"150","qnt":"0"}}'),
('3', '{"26":{"variationOption":"26","productCode":"322992-015","price":"150","qnt":"7"}}');
Use the following query :
SELECT *
FROM `tbl`
where cacheCol REGEXP '.?"qnt":"[1-9]\d*"';
Since the field is always going to be JSON format it is enough to search for the substring alone.
You can play around here
Also it is good idea to explore JSON datatype in Mysql if you would have many updates and reads to this object, if only for simple querying, then you can treat it as string and work with REGEX itself.
Hope it helps

Answer 2

You can use JSON functions like JSON_SEARCH() to find a value that is an exact match, but not a inequality match.
In MySQL 8.0, you can use the JSON_TABLE() function if your JSON were structured as an array, but not with the JSON as you have structured it as an object.
Really, if you need to use inequality expressions to search for specific fields within your data, you should not use JSON at all. You should store the data in normal rows and columns.
The more I see people misusing JSON in complex ways in MySQL, the more I am convinced it was a bad idea for MySQL to implement a JSON data type.
My rule for JSON in MySQL is: references to a JSON column anywhere but the SELECT-list are a code smell. You should use normal columns instead of JSON.

Answer 3

MySQL REGEXP does not support lookaheads, but you can try to achieve the same logic using something like this:
SELECT * FROM "tbl" WHERE ("cacheCol" REGEXP ('(\{[\"\:,\-a-zA-Z0-9]+\"qnt\"\:\"[1-9][0-9]*\"\})'))
Hope it helps.