103

I have started using MySQL 5.7.10 recently and I am liking the native JSON Data type a lot.

But I ran into a problem when it comes to updating a JSON type value.

Questions:

Below is the table format, here I want to add 1 more key in JSON data column for t1 table. Right now I have to fetch the value modify it and Update the table. So it involves an extra SELECT statement.

I can insert like this 

INSERT INTO t1 values ('{"key2":"value2"}', 1);

mysql> select * from t1;
+--------------------+------+
| data               | id   |
+--------------------+------+
| {"key1": "value1"} |    1 |
| {"key2": "value2"} |    2 |
| {"key2": "value2"} |    1 |
+--------------------+------+
3 rows in set (0.00 sec)

mysql>Show create table t1;


+-------+-------------------------------------------------------------

-------------------------------------------------------+
| Table | Create Table                                                                                                       |
+-------+--------------------------------------------------------------------------------------------------------------------+
| t1    | CREATE TABLE `t1` (
  `data` json DEFAULT NULL,
  `id` int(11) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+-------+--------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

Is there a work around for this?

dreftymac
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2 Answers2

164

Thanks @wchiquito for pointing me right direction. I solved the problem. Here is how I did it.

mysql> select * from t1;
+----------------------------------------+------+
| data                                   | id   |
+----------------------------------------+------+
| {"key1": "value1", "key2": "VALUE2"}   |    1 |
| {"key2": "VALUE2"}                     |    2 |
| {"key2": "VALUE2"}                     |    1 |
| {"a": "x", "b": "y", "key2": "VALUE2"} |    1 |
+----------------------------------------+------+
4 rows in set (0.00 sec)

mysql> update t1 set data = JSON_SET(data, "$.key2", "I am ID2") where id = 2;
Query OK, 1 row affected (0.04 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from t1;
+----------------------------------------+------+
| data                                   | id   |
+----------------------------------------+------+
| {"key1": "value1", "key2": "VALUE2"}   |    1 |
| {"key2": "I am ID2"}                   |    2 |
| {"key2": "VALUE2"}                     |    1 |
| {"a": "x", "b": "y", "key2": "VALUE2"} |    1 |
+----------------------------------------+------+
4 rows in set (0.00 sec)

mysql> update t1 set data = JSON_SET(data, "$.key3", "I am ID3") where id = 2;
Query OK, 1 row affected (0.07 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from t1;
+------------------------------------------+------+
| data                                     | id   |
+------------------------------------------+------+
| {"key1": "value1", "key2": "VALUE2"}     |    1 |
| {"key2": "I am ID2", "key3": "I am ID3"} |    2 |
| {"key2": "VALUE2"}                       |    1 |
| {"a": "x", "b": "y", "key2": "VALUE2"}   |    1 |
+------------------------------------------+------+
4 rows in set (0.00 sec)

EDIT: If you want to add an array, use JSON_ARRAY like 

update t1 set data = JSON_SET(data, "$.key4", JSON_ARRAY('Hello','World!')) where id = 2;

enter image description here

Abhinav Kinagi
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    This update working fine for single "key: value" . Then how to update multiple key value?....... – siva Nov 27 '18 at 06:39
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    @siva like this - JSON_SET(@j, '$.key1', 10, '$.key2', '[true, false]') – Snigdha Batra Apr 04 '19 at 07:59
  • how if I want the key from `"$.(:passedData)"` ? I want to update the key based on the value I get from client, it seems that I cannot pass any value thru :passedData – krehwell Jul 15 '20 at 17:23
  • probably better to use set data = IFNULL(JSON_SET(data, "$.key2", "I am ID2"), data) – nvvetal May 18 '22 at 08:20
  • what happened if I don't have any `key` in my column? for e.g: I have this : `["31","32"]` – Shibbir May 20 '22 at 09:04
  • Ah, this worked a treat. It also works with 2D-3D JSON, just supply a daisy-chained key ex $.key1.key2.key3. – Mayur Chauhan Jul 13 '23 at 06:56
20

Now with MySQL 5.7.22+ it is very easy and straightforward to update the whole fragment of json (multiple key values, or even nested) in a single query like this:

update t1 set data = 
JSON_MERGE_PATCH(`data`, '{"key2": "I am ID2", "key3": "I am ID3"}') where id = 2;

Hope it helps someone visiting this page and looking for a "better" JSON_SET :) More about JSON_MERGE_PATCH here: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html#function_json-merge-patch

boryn
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    Also it's worth mentioning that this update does not work if the current `data` is null (and as far as I remember prior to MySQL 8.0.13 you could not set default values to JSON columns). So you might want to do something like `update t1 set data = JSON_MERGE_PATCH(COALESCE(\`data\`, "{}"), '{"key2": "I am ID2", "key3": "I am ID3"}') where id = 2;` – Nimrod Shory Jul 15 '21 at 09:41