Using column alias for calculations in same select list

Question

Hi All,
I want to use a calculated column of query to create further calculated columns in same query using column alias. I have to do so because the calculation is too big to write it everytime.
e.g.
Select decode(Month, 1, Tran_January, 2, Tran_February, ....) as MonthTran,
Month, Year,
round(MonthTran/Intrest_rate, 2) as Amount <---(using previous alias)
from ledger;
Thanks in advance,
Mona

Answer 1

Probably the easiest way of doing this is to write an inline view, viz
SELECT l.Month
       , l.Year
       , round(mt.MonthTran/l.Intrest_rate, 2) AS Amount
FROM   ledger l
       , (SELECT x.pk_col, decode(Month, 1, Tran_January, 2, Tran_February, ....) AS MonthTran
          FROM ledger x) mt
WHERE  l.pk_colunm = mt.pk_colunm
; If you have any criteria in a WHERE clause on ledger you shouldn't need to repeat them providing LEDGER does have a primary key column. You may need to tweak it a bit for performance, if LEDGER is a big table.
Cheers, APC
Cheers, APC