Based on the new information provided by Stellada, the query sould be something like this:
FROM table_a ta JOIN table_b tb
ON ta.acc_number = tb.acc_numer
AND ta.marital_status = tb.new_marital_status
GROUP BY ta.acc_number,ta.name,ta.marital_status;</pre>
If you really want to retrieve only the account number and marital status information, then you would not need to JOIN table_a.
This syntax would work on Oracle 9i or above. On previous versions you would need to use the old syntax to join tables in the WHERE clause.