Sådan indsætter du poster fra tabel til en anden uden duplikat

insert into test.t2(name2) 
select distinct name1 from test.t1 where name1 NOT IN(select name2 from test.t2);

ELLER

insert into test.t2(name2) 
select distinct name1 from test.t1 t1 where NOT EXISTS(select name2 from test.t2 t2 where t1.name1=t2.name2);