MySQL Update or Rename a Key in JSON

I personally prefer another method:

UPDATE my_table SET my_col = REPLACE(my_col, '"oldKeyValue":', '"newKeyValue":')

This replaces directly the key name in the JSON string without destroying the JSON structure.

I am using the additional : in order to avoid an unintentional replacement in a value.

There is no straightforward JSON function to do the same. We can use a combination of some JSON functions.

We will remove the oldKey-oldValue pair using Json_Remove() function, and then Json_Insert() the newKey-oldValue pair.

Json_Extract() function is used to fetch value corresponding to an input key in the JSON document.

UPDATE `my_table` 
SET `my_col` = JSON_INSERT(
                           JSON_REMOVE(my_col, '$.oldKeyValue'), 
                           '$.newKeyValue', 
                           JSON_EXTRACT(my_col, '$.oldKeyValue')
                          );

Demo

SET @my_col := '{"endDate": "2018-10-10", "startDate": "2017-09-05", "oldKeyValue": {"foo": 1000, "bar": 2000, "baz": 3000}, "anotherValue": 0}';

SET @new_col := JSON_INSERT(
                            JSON_REMOVE(@my_col, '$.oldKeyValue'), 
                            '$.newKeyValue',
                            JSON_EXTRACT(@my_col,'$.oldKeyValue')
                          );

SELECT @new_col;

Result

| @new_col                                                                                                                        |
| ------------------------------------------------------------------------------------------------------------------------------- |
| {"endDate": "2018-10-10", "startDate": "2017-09-05", "newKeyValue": {"bar": 2000, "baz": 3000, "foo": 1000}, "anotherValue": 0} |

---

As an alternative to Json_Extract(), we can also use -> operator to access the Value corresponding to a given Key in the JSON doc.

UPDATE `my_table` 
SET `my_col` = JSON_INSERT(
                           JSON_REMOVE(my_col, '$.oldKeyValue'), 
                           '$.newKeyValue', 
                           my_col->'$.oldKeyValue' 
                          );