drop table if exists t2;
create table t2 (i int primary key, j int);
insert into t2 values (1,1),(2,2),(5,null),(4,4),(3,3);
select * from t2 where (i) in ((1),(null)) and i = 2;
i	j
select * from t2 where (i) in ((1),(null)) and i = 1;
i	j
1	1
select * from t2 where (i) in ((1),(null));
i	j
1	1
select * from t2 where (i) in ((1),(null)) and i = 1 and i = 2;
i	j
update t2 set j=i+1 where i=2;
select * from t2;
i	j
1	1
2	3
3	3
4	4
5	NULL
drop table t2;