String conversion gives error when converting to date format

Question

Hello,
I need to convert a character to a date format. The character string is 201053131415151 where the first eight characters represent YYYYMMDD. The string may also be null ( second value). I used the following select statement
select distinct sysdate "Run Date",
rcreviewdate "Review Date",
nvl((to_char(substr(rcreviewdate,1,8))),'None') "Review Date2"
and got the following result.
Run Date Review Date Review Date2
30-NOV-09 201005131415151 20100513
30-NOV-09
1. Why is "None" not returned for the secord valule which is null?
2. How can the valule "20100513" be converted to DD-MON-YY ( the date format)?
to_date(substr(rcreviewdate,1,8),'YYYYMMDD') gives the following error with the null value
Error report:
SQL Error: ORA-01841: (full) year must be between -4713 and +9999, and not be 0
01841. 00000 - "(full) year must be between -4713 and +9999, and not be 0"

Answer 1

Hi,
PANY wrote:
1. Why is "None" not returned for the secord valule which is null?
2. How can the valule "20100513" be converted to DD-MON-YY ( the date format)?
to_date(substr(rcreviewdate,1,8),'YYYYMMDD') gives the following error with the null value
Error report:
SQL Error: ORA-01841: (full) year must be between -4713 and +9999, and not be 0
01841. 00000 - "(full) year must be between -4713 and +9999, and not be 0"Are you sure reviewdate is NULL, and not a string consisting only of spaces or tabs?
TO_DATE will return NULL if its 1st argument is NULL, so it looks like reviewdate is not NULL.
You can use LTRIM (among other functions) to remove spaces from reviewdate, if that's the problem.
Post a little sample data (CREATE TABLE and INSERT statements), and the results you want from that data.