Date from Day number and year

Question

Dear experts,
i have day number and year ,i wanted to identify the date
ex: day number=203 year=2009
date:22/07/2009
please advice the best possible way to acheive this.
thanks

Answer 1

Florian:
Given that the OP said his fields were VARCHAR2, and his sample data showed leading zeroes, your original solution will work as posted. If the data had been numeric, another solution would be to just reverse the order of the components.
SQL> WITH t AS (
  2     SELECT 2009 yr, 203 day_no FROM dual union all
  3     SELECT 2006, 201 FROM dual union all
  4     SELECT 1999,  99 FROM dual union all
  5     SELECT 2000, 001 FROM dual union all
  6     SELECT 1945, 100 FROM dual union all
  7     SELECT 1921, 101 FROM dual)
  8  SELECT TO_DATE(yr||day_no, 'yyyyddd') dt FROM t;
DT
22-JUL-2009
20-JUL-2006
09-APR-1999
01-JAN-2000
10-APR-1945
11-APR-1921It is the way that format masks are applied that causes his. With your mask and numeric iinput, it is taking the first 3 digits as the day number, in your example 902, then the remainder of them as the year, in your example 9. Obviously, the number of days in a year is never more than 366.
By reversing the mask, the first 4 digits are taken as the year, and the remainder are taken as the day number.
John