MySQL:

JSON_MERGE

Syntax:
JSON_MERGE(json_doc, json_doc[, json_doc] ...)

Merges two or more JSON documents. Synonym for JSON_MERGE_PRESERVE();
deprecated in MySQL 8.0.3 and subject to removal in a future release.

URL: https://dev.mysql.com/doc/refman/8.0/en/json-modification-functions.html

Example

mysql> SELECT JSON_MERGE('[1, 2]', '[true, false]');
+---------------------------------------+
| JSON_MERGE('[1, 2]', '[true, false]') |
+---------------------------------------+
| [1, 2, true, false] |
+---------------------------------------+
1 row in set, 1 warning (0.00 sec)

mysql> SHOW WARNINGS\G
*************************** 1. row ***************************
Level: Warning
Code: 1287
Message: 'JSON_MERGE' is deprecated and will be removed in a future release. \
Please use JSON_MERGE_PRESERVE/JSON_MERGE_PATCH instead
1 row in set (0.00 sec)