CREATE TABLE t5 (
 col1 VARCHAR(36) NOT NULL PRIMARY KEY,
 col2 int(11) DEFAULT NULL,
 col3 int(11) DEFAULT NULL,
 UNIQUE (col2)
);

insert into t5(col1, col2, col3) values
('872c18ba-35ae-11e9-91a5-88d7f65253d0', 1, 1),
('823c3d3a-35ae-11e9-91a5-88d7f65253d0', 2, 2);

insert into t5(col1, col2, col3) values
 ('872c18ba-35ae-11e9-91a5-88d7f65253d0', 2, 888),
 ('823c3d3a-35ae-11e9-91a5-88d7f65253d0', NULL, 999),
on duplicate key update
 col2=if(values(col2) IS NULL, col2, values(col2)),
 col3=if(values(col3) IS NULL, col3, values(col3));

update t5 set
 col2=(case col1 when '872c18ba-35ae-11e9-91a5-88d7f65253d0' then 2 END)
 col3=(case col1 when '872c18ba-35ae-11e9-91a5-88d7f65253d0' then 888 when '823c3d3a-35ae-11e9-91a5-88d7f65253d0' then 999 END)
where col1 in ('872c18ba-35ae-11e9-91a5-88d7f65253d0', '823c3d3a-35ae-11e9-91a5-88d7f65253d0');