MySQL JSON: Searching Objects Based on Key Values

MySQL tables often utilize JSON columns to store complex data structures. When working with JSON, a common task is to retrieve a specific object based on a key-value pair. However, finding the object directly may not always be straightforward.

JSON Schema Example:

Consider the following schema:

CREATE TABLE `fields` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `label` varchar(64) COLLATE utf8mb4_unicode_ci NOT NULL,
  `options` json DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

With sample data:

INSERT INTO `fields` (label, options) VALUES
(
  'My Field', 
  '[{"text": "Grass", "value": "1"}, {"text": "Synthetic (New Type - Soft)", "value": "2"}, {"text": "Synthetic  (Old Type - Hard)", "value": "3"}, {"text": "Gravel", "value": "5"}, {"text": "Clay", "value": "6"}, {"text": "Sand", "value": "7"}, {"text": "Grass/Synthetic Mix", "value": "8"}]'
);

Problem:

Suppose we want to retrieve the string "Grass" from the options JSON array, knowing that its corresponding "value" is "1." Using JSON_EXTRACT() alone requires the index of the array, which may not be readily available.

Solution 1: Using JSON_SEARCH() and Horrible String Manipulation

This approach combines JSON_SEARCH() to partially find the index and then removes unwanted parts from the string:

SELECT
JSON_EXTRACT(`options`,CONCAT('$[',REPLACE(REPLACE(JSON_SEARCH(`options`, 'one', '1'), '"$[', ''), '].value"', ''), '].text'))
from `fields`;

Solution 2: Using JSON_TABLE()

MySQL 8.0 introduces JSON_TABLE() to simplify this task:

select field_options.* from fields cross join 
json_table(fields.options, 
'$[*]' columns(
  text text path '$.text',
  value text path '$.value'
 )
) as field_options 
where field_options.value = 1;

Alternative Approach: Relational Data Model

For simpler data structures like this example, consider storing the data in a relational table with columns for key and value pairs, allowing for direct search:

SELECT * FROM field_options WHERE value = '1';