MariaDB 10.4

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CREATE TABLE user (id INT PRIMARY KEY,
                   fname VARCHAR(64),
                   lname VARCHAR(64),
                   age INT);
INSERT INTO user VALUES
(1, 'Vassily', 'Pupkin', 20),
(2, 'idiosinkrazy', 'Ziper-Molnienossny', 25);
SELECT * FROM user;


id
fname
lname
age


1
Vassily
Pupkin
20

2
idiosinkrazy
Ziper-Molnienossny
25


SET @parameters := '{"id":1,"fname":"Vasily","age":21}';
UPDATE user
SET fname = COALESCE(JSON_UNQUOTE(JSON_EXTRACT(@parameters, "$.fname")), fname),
    lname = COALESCE(JSON_UNQUOTE(JSON_EXTRACT(@parameters, "$.lname")), lname),
    age = COALESCE(JSON_EXTRACT(@parameters, "$.age"), age)
WHERE id = JSON_EXTRACT(@parameters, "$.id");
SELECT * FROM user;


id
fname
lname
age


1
Vasily
Pupkin
21

2
idiosinkrazy
Ziper-Molnienossny
25