drop table if exists t1;
create table t1(pk int primary key, c1 int);
insert into t1 values(1,1);
begin;
select *  from t1   where pk=1 for update;
pk	c1
1	1
update t1 set c1=c1+1 where pk=1;
begin;
select *  from t1  where t1.pk=1 for update;
commit;
pk	c1
1	2
update t1 set c1=c1+1 where pk=1;
commit;
select * from t1;
pk	c1
1	3