drop table if exists t1, t2, t3;
create table t1 (_id int, c1 int, key (_id) using hash);
insert into t1 values(null, 100);
insert into t1 values(null, 100);
insert into t1 values(null, 100);
insert into t1 values(null, 100);
select * from t1;
_id	c1
1	100
2	100
3	100
4	100
update t1 set c1 = 200 where _id = 2;
select * from t1;
_id	c1
1	100
2	200
3	100
4	100
drop table t1;
