sql join

Hello,

I have two tables, tableA, tableB. tableA has userid, memberid columns with a total count of 300. tableB has userid, address columns. I have a flat file with memberid and address columns with around 6000 records. I need to update tableB's address column (all rows that currently have null address) using tableA and the flatfile. I believe the first step is to create a temp table tableC(from flatfile) in the database. Is it something that can be done with sql? If I have to use pl/sql, could you suggest a good approach? Thanks in advance

Could you pl post the table creation scripts ?
That would be much helpful for others to reply to your question.

Tamil