As a part from my new project, I'm using MySQL JSON field which was introduced in version 5.7, functions are described in https://dev.mysql.com/doc/refman/5.7/en/json-functions.html Creating JSON data is pretty simple like: 

CREATE TABLE `events` (
	`id` INT(11) NOT NULL AUTO_INCREMENT,
	`site_id` INT(11) NOT NULL,
	`category_id` INT(11) NOT NULL,
	`name` VARCHAR(250) NOT NULL,
	`value` TEXT NULL,
	`added_time` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
	`custom_data` JSON NULL DEFAULT NULL,
	PRIMARY KEY (`id`),
	INDEX `site_id` (`site_id`, `category_id`)
)
COLLATE='utf8_general_ci'
ENGINE=InnoDB
AUTO_INCREMENT=0;
As you can see Create Table syntax is same, difference is in 
 `custom_data` JSON
. So let's insert some data to it. 
INSERT INTO `events` (`id`, `site_id`, `category_id`, `name`, `value`, `added_time`, `custom_data`) VALUES (3, 1, 4, 'fsafsa', '21', '2015-12-21 23:05:56', NULL);
INSERT INTO `events` (`id`, `site_id`, `category_id`, `name`, `value`, `added_time`, `custom_data`) VALUES (4, 1, 4, 'fsafsa', '21', '2015-12-21 23:06:09', NULL);
INSERT INTO `events` (`id`, `site_id`, `category_id`, `name`, `value`, `added_time`, `custom_data`) VALUES (5, 1, 4, 'fsafsa', '2кири', '2015-12-21 23:06:16', NULL);
INSERT INTO `events` (`id`, `site_id`, `category_id`, `name`, `value`, `added_time`, `custom_data`) VALUES (6, 1, 4, 'fsafsa', '2кири', '2015-12-25 10:11:54', '{"dada": {"rpb": "22"}, "test": "dada"}');
INSERT INTO `events` (`id`, `site_id`, `category_id`, `name`, `value`, `added_time`, `custom_data`) VALUES (7, 1, 1, 'test', '1', '2015-12-25 17:26:04', NULL);
INSERT INTO `events` (`id`, `site_id`, `category_id`, `name`, `value`, `added_time`, `custom_data`) VALUES (8, 1, 1, '1da', '2', '2015-12-25 17:26:10', '{"test": "dada"}');

And lets assume that we want to filter data in JSON field. 
SELECT  id,custom_data FROM `events` WHERE JSON_UNQUOTE(custom_data->"$.test") = "dada"
Result is: 
+----+-----------------------------------------+
| id | custom_data                             |
+----+-----------------------------------------+
|  6 | {"dada": {"rpb": "22"}, "test": "dada"} |
|  8 | {"test": "dada"}                        |
+----+-----------------------------------------+
2 rows in set (0.00 sec)
Or if we want to check existence of sub element: 
SELECT id,custom_data  FROM `events` WHERE  JSON_CONTAINS_PATH(custom_data,"all","$.dada.rpb");
Result is: 
+----+-----------------------------------------+
| id | custom_data                             |
+----+-----------------------------------------+
|  6 | {"dada": {"rpb": "22"}, "test": "dada"} |
+----+-----------------------------------------+
1 row in set (0.00 sec)
And one more example for extracting value from JSON: 
SELECT 
	id,
	JSON_UNQUOTE(JSON_EXTRACT(custom_data,'$.test')) AS value
FROM `events`
WHERE JSON_EXTRACT(custom_data,'$.test') IS NOT NULL

+----+-------+
| id | value |
+----+-------+
|  6 | dada  |
|  8 | dada  |
+----+-------+
2 rows in set (0.00 sec)

It's look pretty easy, right ? :)