What is "data"? If you mean column, what is its data type? Can you post some sample values?
What "data" is "13 digits"? May they be separated/padded by another characters?
Maybe it would be helpful, if you read this article before posting any question:
http://tkyte.*************/2005/06/ho...questions.html
Pay special attention to the "Context" paragraph. Then, please try to post relevant parts of your problem. Do not hesitate to also post DDL/DML statements - yes, we do understand Oracle SQL here.
Because, now it is impossible to deduce anything (input, applied rules, output) from your post, so it is also impossible to provide you any meaningful suggestion/solution.