How to get values from MySQL(5.6) column if that contains json document as string

Question

How to get values from MySQL(5.6) column if that contains JSON document as a string

For example, if we have a table - employee in that we have three columns id, nam

Answer 1

Below answer works for me. it remove double quotes from the value.

DELIMITER $$

DROP FUNCTION IF EXISTS `json_extract_values`$$

CREATE DEFINER=`root`@`localhost` FUNCTION `json_extract_values`(
  details TEXT,
  required_field VARCHAR (255)
) RETURNS TEXT CHARSET latin1
BEGIN
SET details = SUBSTRING_INDEX(details, "{", -1);
SET details = SUBSTRING_INDEX(details, "}", 1);
RETURN 
    SUBSTRING_INDEX(
        TRIM(
            TRAILING '"' FROM 
                SUBSTRING_INDEX(
                    details,
                    CONCAT( 
                           '"', 
                           SUBSTRING_INDEX(required_field,'$.', - 1),
                           '":'
                          ),
                -1 )
            ),
        '"',
     -1);    
END$$

DELIMITER ;

Answer 2

To be able to do what you want to, you need MySQL 5.7.8+. Since 5.7.8 you can use JSON_EXTRACT function to extract a value from a JSON string:

SELECT JSON_EXTRACT('{"id": 14, "name": "Aztalan"}', '$.name');

+---------------------------------------------------------+
| JSON_EXTRACT('{"id": 14, "name": "Aztalan"}', '$.name') |
+---------------------------------------------------------+
| "Aztalan"                                               |
+---------------------------------------------------------+

Taken from here.

In MySQL 5.6 you just can't get the value you want as MySQL doesn't know anything about what a JSON object is. So your options are:

• Upgrade to 5.7.8+
• Parse the query result with something that handles JSON:
  • Could be PHP json_decode (or equivalent in your language)
  • An online tool like http://json.parser.online.fr/

Answer 3

Both previous answers didn't work for me when the element wasn't mentioned in JSON text. There is my improved function:

DELIMITER $$

DROP FUNCTION IF EXISTS `json_extract_c`$$

CREATE FUNCTION `json_extract_c`(
details TEXT,
required_field VARCHAR (255)
) RETURNS TEXT CHARSET latin1
BEGIN
  DECLARE search_term TEXT;
  SET details = SUBSTRING_INDEX(details, "{", -1);
  SET details = SUBSTRING_INDEX(details, "}", 1);
  SET search_term = CONCAT('"', SUBSTRING_INDEX(required_field,'$.', - 1), '"');
  IF INSTR(details, search_term) > 0 THEN
    RETURN TRIM(
      BOTH '"' FROM SUBSTRING_INDEX(
        SUBSTRING_INDEX(
          SUBSTRING_INDEX(
            details,
            search_term,
            - 1
          ),
          ',"',
          1
        ),
        ':',
        -1
      )
    );
  ELSE
    RETURN NULL;
  END IF;
END$$

DELIMITER ;

Answer 4

In MySQL 5.6, by default JSON_EXTRACT is not available by default.
If you still need to access json data in MySQL 5.6, you need to write custom function.

DELIMITER $$

DROP FUNCTION IF EXISTS `json_extract_c`$$

CREATE DEFINER=`root`@`%` FUNCTION `json_extract_c`(
  details TEXT,
  required_field VARCHAR (255)
) RETURNS TEXT CHARSET latin1
BEGIN
  RETURN TRIM(
    BOTH '"' FROM SUBSTRING_INDEX(
      SUBSTRING_INDEX(
        SUBSTRING_INDEX(
          details,
          CONCAT(
            '"',
            SUBSTRING_INDEX(required_field,'$.', - 1),
            '"'
          ),
          - 1
        ),
        '",',
        1
      ),
      ':',
      - 1
    )
  ) ;
END$$

DELIMITER ;

This will help. I have created it and tested.