Query one of the twos

Question

I have a table (tbl1) as follows:
col1      col2      col3
1111      CM      XXXX
1111      ML      XXXX
1111      AB      XXXX
2222      ML      XXXX
2222      AB      XXXX
From the above table, how do I retrieve a record according to the following criteria?
Retrieve the record where col2 = 'CM'. If 'CM' is not available for a record retrieve the record where col2 is 'ML'. From the above data, I am supposed to be getting only the one record with 'CM' for '1111' and the one with 'ML' for '2222'. I am not sure how this can be achieved. If I use DECODE, the problem is, I am getting 2 records for col1 = '1111', since both 'CM' and 'ML' are present for the col1 = '1111'.
Is there a better way to do this query?

Answer 1

SQL> create table aron.tbl1(col1 number, col2 varchar2(2), col3 varchar2(5))
Table created
SQL> insert into aron.tbl1 values(1111, 'CM', 'XXXX')
1 row inserted
SQL> insert into aron.tbl1 values(1111, 'ML', 'XXXX')
1 row inserted
SQL> insert into aron.tbl1 values(1111, 'AB', 'XXXX')
1 row inserted
SQL> insert into aron.tbl1 values(2222, 'ML', 'XXXX')
1 row inserted
SQL> insert into aron.tbl1 values(2222, 'AB', 'XXXX')
1 row inserted
SQL> select *
from (select t.*, rank() over (partition by col1 order by col1, col2) r
     from aron.tbl1 t
     where col2 in ('CM', 'ML')
where r = 1
      COL1 COL2 COL3           R
      1111 CM   XXXX           1
      2222 ML   XXXX           1
2 rows selected