Question

select * from table1 where destination in  ('chi','usa','ind')

Ideally my result set should be 3 rows. one row for each destination.

But in my result there are duplicates.

chi
usa
ind
usa

I want to find which destination is duplicated.
I have hundreds of destination and i want to delete the duplicate records.
I am not looking for distinct. Am looking for the duplicated ones.

Answer 1

Use group by and having instead of distinct

select destination from table1 
where destination in  ('chi','usa','ind')
group by destination 
having count(*)>1

If you want to delete these and retain one, it gets a little messy. This is probably the shortest way, but its a bit of a hack.

delete from destination where id not in (
    select max(id) from table1
      where destination in  ('chi','usa','ind')
      group by destination 
    )