Different Criteria same field select?

Question

New to straight Oracle SQL, I come from a programming background using MySQL. I’m going to smipify this a lot and changed table and field names and such to protect the identity of the innocent tables...jk
BOOKS has an b_id and b_name =>(book id and name).
1234, Old man and the Sea
2345, War of the Worlds
TRANSACTIONS has b_id, key_code and date.
1234, TT3, 15-Feb-09
1234, A890, 01-jan-09
1234, A456, 11-jan-89
2345, TT3, 5-may-09
1234, Z80, 25-oct-07
2345, Z80, 25-Nov-07
What I need to do is for each book that has a TT3 transaction; find the Z80 transaction and find how many days passed between the two transactions. I could do this so easy in program but I’m not sure how to do in a select. Thanks in advance.

Answer 1

with books as (
               select 1234 b_id,'Old man and the Sea' b_name from dual union all
               select 2345,'War of the Worlds' from dual
       trn as (
               select 1234 b_id,'TT3' key_code,to_date('15-Feb-09','dd-mon-yy') dt from dual union all
               select 1234,'A890',to_date('01-jan-09','dd-mon-yy') from dual union all
               select 1234,'A456',to_date('11-jan-89','dd-mon-yy') from dual union all
               select 2345,'TT3',to_date('5-may-09','dd-mon-yy') from dual union all
               select 1234,'Z80',to_date('25-oct-07','dd-mon-yy') from dual union all
               select 2345,'Z80',to_date('25-Nov-07','dd-mon-yy') from dual
select  distinct b_name,
                 b.b_id,
                 abs(next_dt - dt) days_between_tansactions
  from  (
         select  b_id,
                 key_code,
                 lead(key_code) over(partition by b_id order by dt) next_key_code,
                 dt,
                 lead(dt) over(partition by b_id order by dt) next_dt
           from  trn
           where key_code in ('TT3','Z80')
        ) t,
        books b
  where b.b_id = t.b_id
    and (
            (key_code = 'TT3' and next_key_code = 'Z80')
         or
           (key_code = 'Z80' and next_key_code = 'TT3')
B_NAME                    B_ID DAYS_BETWEEN_TANSACTIONS
Old man and the Sea       1234                      479
War of the Worlds         2345                      527
SQL> SY.