MySQL 8.0

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CREATE TABLE t1 (id INT, `group` VARCHAR(255), names JSON);
INSERT INTO t1 VALUES
(1100000, 'group1', '[{"name": "name1", "type": "user"}, {"name": "name2", "type": "user"}, {"name": "techDept", "type": "dept"}]');
SELECT * FROM t1;


id
group
names


1100000
group1
5b7b226e616d65223a20226e616d6531222c202274797065223a202275736572227d2c207b226e616d65223a20226e616d6532222c202274797065223a202275736572227d2c207b226e616d65223a20227465636844657074222c202274797065223a202264657074227d5d


SET @userlist = '["user4", "user5"]';
UPDATE t1
JOIN ( SELECT JSON_ARRAYAGG(JSON_OBJECT('name', username, 'type', 'user')) userlist
       FROM JSON_TABLE (@userlist,
                        '$[*]' COLUMNS (username VARCHAR(255) PATH '$')) jsontable ) jsontable
SET t1.names = JSON_MERGE_PRESERVE(t1.names, jsontable.userlist)
WHERE t1.`group` = 'group1';

Rows matched: 1  Changed: 1  Warnings: 0


SELECT * FROM t1;


id
group
names


1100000
group1
5b7b226e616d65223a20226e616d6531222c202274797065223a202275736572227d2c207b226e616d65223a20226e616d6532222c202274797065223a202275736572227d2c207b226e616d65223a20227465636844657074222c202274797065223a202264657074227d2c207b226e616d65223a20227573657234222c202274797065223a202275736572227d2c207b226e616d65223a20227573657235222c202274797065223a202275736572227d5d