CASE in the FROM clause ?

Question

Hello, I need to query a table which (unfortunately) its name is depended on the date. (Year, Month, and every 15 days (Fortnight FN)
My tables is STAT_VEHICLES_YY_MM and if it refers to the fortnight report it becomes STAT_VEHICLES_YY_MM15
For example this fortnight (15 of July report) will be STAT_VEHICLES_09_0815 and the 1st of this month report was on STAT_VEHICLES_09_08 table.
My query so far is:
ACCEPT YY prompt 'Please enter current year in YY format:'
ACCEPT MM prompt 'Please enter current month in the MM format:'
SELECT COUNT(*) "STAT VEH. NEW LIC."
FROM STAT_VEHICLES_&YY._&MM
WHERE NR=3;
I tried using something like
ACCEPT FN prompt 'Is this a fortnight report? (Y/N): '
SELECT…
FROM
CASE
WHEN &FN = Y THEN STAT_VEHICLES_&YY._&MM.15
WHEN &FN = y THEN STAT_VEHICLES_&YY._&MM.15
WHEN &FN = N THEN STAT_VEHICLES_&YY._&MM
WHEN &FN = n THEN STAT_VEHICLES_&YY._&MM
END
WHERE…
But I don’t think that CASE will work in the FROM clause
My next though is OUTER JOIN and here is where I need your help people.
Thank you

Answer 1

Obviously this is extreemly poor design, and it should have been implemented by partitioning 1 table.
In that case Oracle would have automatically choosen the right partition!!!
What you can do is
column table_name new_value tablename
ACCEPT YY prompt 'Please enter current year in YY format:'
ACCEPT MM prompt 'Please enter current month in the MM format:'
select stat_vehicles_&YY._&MM table_name
from dual;
select count(*)
from &_table_name
where nr=3;
You would need to use &_table_name everywhere.
Hth
Sybrand Bakker
Senior Oracle DBA