How should I do??

Question

In my program I have to do a part which I first need to export the data from some tables, which is located from 1 server, then import again, which is into another server.
If its only for inserting the data I should have no problem. But now, I need to cater for both inserting new data and updating existing data. So, to do update I need to find the primary keys for each table then find a way to run the update statement. I am using oracle 8.1.7.
So here's my problem, How can I get the primary key from oracle?? I've tried searching around the database but can't find the table that stores all the primary key records. Besides, can I try to get the primary key from java without making a text file of primary keys manually??
On the other hand, I have no experience of doing such program to import & export, so I kindly ask the experts here how do you usually carry out such process??
Thanks.

Answer 1

If this is professional work, you should look at the Oracle utility programs "exp" and "imp" (or "expdp" and "impdp", if you are using Oracle 10g); they're always going to be faster than practically anything you can write yourself. They're documented in the "Utilities" book for your version of the database, which is online.
Start with http://www.oracle.com/technology/documentation/index.html
Select your version of the databse. Click on "View Library".
Get the list of books. Select the Utilities book.
There are also a large number of Oracle technolgies for moving data between databases: Oracle Streams, Data Guard/standby database, materialized views, database links, log miner, etc. All of these are documented/explained in the documentation on Oracle's site (and have nothing to do with Java/JDBC).
If you have to do it in Java, you can get all sorts of information about the databse using the DatabaseMetaData class. Oracle databases also have a set of system-maintained views which have all the information about the data dictionary that is available; these have names which begin with ALL_ and USER_, such as ALL_TABLES and USER_CONSTRAINTS. You can get a list of them with:
SELECT view_name FROM all_views where view_name like ('USER_%') order by 1;
There are also explanations of most of the useful ones on the web; use Google.
Good luck.