Query on Join.

Question

I have two tables...
in 1st table lets say emp_sal i have employees salary date wise.
for eg:
100 20 01-APR-2010
102 15 01-APR-2010
100 30 02-APR-2010
I need a query where i will give parameter From date and to_date it should return all emplyees sal and missing salary should return as 0
For eg... if is give 01-APR-10 as from date and 02-APR-10 as to date it should return
100 20 01-APR-2010
102 15 01-APR-2010
100 30 02-APR-2010
102 0 02-APR-2010
Pls help

Answer 1

Partitioned outer join would be perfect here:
with emp_sal as (select 100 empno, 20 salary, to_date('01/04/2010', 'dd/mm/yyyy') dt from dual union all
                 select 102 empno, 15 salary, to_date('01/04/2010', 'dd/mm/yyyy') dt from dual union all
                 select 100 empno, 30 salary, to_date('02/04/2010', 'dd/mm/yyyy') dt from dual),
-- end of mimicking your data in a subquery called emp_sal. Hurrah for subquery factoring!
       dates as (select to_date('01/04/2010', 'dd/mm/yyyy') + level -1 dt  -- replace the dates with your from_date/to_date parameters
                 from   dual
                 connect by level <= to_date('02/04/2010', 'dd/mm/yyyy') - to_date('01/04/2010', 'dd/mm/yyyy') + 1)     
select es.empno, nvl(es.salary, 0) salary, dates.dt
from   dates
       left outer join emp_sal es partition by (es.empno) on (dates.dt = es.dt);
     EMPNO     SALARY DT       
       100         20 01/04/2010
       100         30 02/04/2010
       102         15 01/04/2010
       102          0 02/04/2010