drop table if exists t;
create table t (c1 int primary key, c2 int);
insert into t values(1,2),(3,4),(1,2);
ERROR 23000: Duplicate entry '1' for key 'PRIMARY'
insert into t values(1,2),(3,4),(5,6);
select * from t;
c1	c2
1	2
3	4
5	6
select * from t where c1 in (1,3,1);
c1	c2
1	2
3	4
select * from t where c1 in (1,1);
c1	c2
1	2
drop table t;