How to extract data from Mysql column stored in serialized JSON column? - mysql

Question

I have column in mysql DB which contains serialized data (used PHP JSON encode to serialize them).
Here is an example:
{"name":"Group ltd","email":"support#domain.org","auth":"Andrey Ucholnik"}
Is there a built in function in mysql to extract these values without PHP ?
I mean to build query that will unserialize data.
Of course its possible to use combination of LOCATE and SUBSTR function to do that but I prefer something built in if possible.

Answer 1

There is no build in function in MySQL but by using small code in PHP you can easily do it as under:
<?php
$json = '{{"generated": "2010-02-26T22:26:03.156866 blahblahblah ": null, "thumbnail_url": "http://thumbs.mochiads.com/c/g/tetword-pro/_thumb_100x100.jpg", "screen4_url": "http://thumbs.mochiads.com/c/g/tetword-pro/screen4.png", "leaderboard_enabled": true, "resolution": "600x550", "width": 600}]}}';
$out = json_decode($json, true);
foreach($out["games"] as $game) {
$name = addslashes($game[name]);
$description = addslashes($game[description]);
//Here you can use your mysql_insert code
mysql_query("INSERT INTO games (name, description) VALUES('$name', '$description')") or die (mysql_error());
}
?>

Answer 2

There are no built-in MySQL functions to work with JSON, but here is a very simple stored function to extract values from JSON:
DELIMITER $$
CREATE FUNCTION JSON_EXTRACT(json TEXT, name CHAR(64))
RETURNS CHAR(64) DETERMINISTIC
BEGIN
SET #namePos = LOCATE(name, json);
IF #namePos = 0 THEN RETURN ''; END IF;
SET #valuePos = LOCATE(':', json, #namePos) + 1;
IF SUBSTR(json, #valuePos, 1) = '"' THEN
SET #valuePos = #valuePos + 1;
RETURN SUBSTR(json, #valuePos, LOCATE('"', json, #valuePos) - #valuePos);
ELSE
SET #valueBegin = TRIM(SUBSTR(json, #valuePos));
SET #delim1 = LOCATE(' ', #valueBegin); SET #delim1 = IF(#delim1 = 0, 64, #delim1);
SET #delim2 = LOCATE(',', #valueBegin); SET #delim2 = IF(#delim2 = 0, 64, #delim2);
SET #delim3 = LOCATE('}', #valueBegin); SET #delim3 = IF(#delim3 = 0, 64, #delim3);
RETURN LEFT(#valueBegin, LEAST(#delim1, #delim2, #delim3) - 1);
END IF;
END$$
Usage example:
SELECT JSON_EXTRACT('{"a":"aa","b" : 1, "c": 3}', 'b') AS test;
Note that the function has many limitations. For example, it doesn't handle nested classes and key names shouldn't be included in the values.

Answer 3

Yes , you can definitely to it using JSON_EXTRACT() function in mysql.
lets take a table that contains JSON (table client_services here) :
+-----+-----------+--------------------------------------+
| id | client_id | service_values |
+-----+-----------+------------+-------------------------+
| 100 | 1000 | { "quota": 1,"data_transfer":160000} |
| 101 | 1000 | { "quota": 2,"data_transfer":800000} |
| 102 | 1000 | { "quota": 3,"data_transfer":70000} |
| 103 | 1001 | { "quota": 1,"data_transfer":97000} |
| 104 | 1001 | { "quota": 2,"data_transfer":1760} |
| 105 | 1002 | { "quota": 2,"data_transfer":1060} |
+-----+-----------+--------------------------------------+
To Select each JSON fields , run this query :
SELECT
id, client_id,
json_extract(service_values, '$.quota') AS quota,
json_extract(service_values, '$.data_transfer') AS data_transfer
FROM client_services;
So the output will be :
+-----+-----------+----------------------+
| id | client_id | quota | data_transfer|
+-----+-----------+----------------------+
| 100 | 1000 | 1 | 160000 |
| 101 | 1000 | 2 | 800000 |
| 102 | 1000 | 3 | 70000 |
| 103 | 1001 | 1 | 97000 |
| 104 | 1001 | 2 | 1760 |
| 105 | 1002 | 2 | 1060 |
+-----+-----------+----------------------+
Hope this helps!