如何以准备好的语句更新mysql 5.7中json列中的键的动态数目

Question

I have created a table in MySQL 5.7 like below.

id   :int
data :json

Now data has multiple keys as json.

data = {"a":"b","c":"d"};

Now I have a requirement to update existing data with new data for an update multiple(dynamic) keys in it.

How to achieve this.

Answer 1

You may simply run an UPDATE query by setting the updated object in stringfied form.

For example: Considering you are building a JS application.

updatedData = JSON.Stringify(updatedData)

query> update t set data = updatedData;

Answer 2

Here's a demo. First I create a table like yours with JSON data.

mysql [localhost] {msandbox} (test) > create table t (id int primary key, data json);
Query OK, 0 rows affected (0.02 sec)

mysql [localhost] {msandbox} (test) > insert into t values (1, json_object('a', 'b', 'c', 'd'));
Query OK, 1 row affected (0.01 sec)

mysql [localhost] {msandbox} (test) > select * from t;
+----+----------------------+
| id | data                 |
+----+----------------------+
|  1 | {"a": "b", "c": "d"} |
+----+----------------------+
1 row in set (0.00 sec)

Now I update the JSON data with new values.

mysql [localhost] {msandbox} (test) > update t set data = json_merge_patch(data, json_object('a', 123, 'c', 'foo'));
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql [localhost] {msandbox} (test) > select * from t;
+----+------------------------+
| id | data                   |
+----+------------------------+
|  1 | {"a": 123, "c": "foo"} |
+----+------------------------+

For a prepared statement, you should use parameter placeholders as you create the JSON object that will update the data.

update t set data = json_merge_patch(data, json_object(?, ?, ?, ?));

I'm not sure what you mean by dynamic keys. You will have to use parameter placeholders in pairs (1 key, 1 value), and the number of parameters needs to be fixed at the time you prepare the query. It's up to you to write application code to build the query with as many parameter placeholders as you need.

You should read about JSON functions like JSON_MERGE_PATCH() here: https://dev.mysql.com/doc/refman/5.7/en/json-modification-functions.html