MySQL SUM – Adding a New Value to an Existing Value

Changing the data type of a column causes a table restructure, which will have the side-effect of rebuilding all indexes for the table (not only those referencing the column you altered, but all indexes in that table).

You don't need to drop or recreate the indexes yourself; it's already done by the time the ALTER TABLE finishes.

Try using heterogenous Connectivity to link the Oracle database to the mySQL database. It would be easier to directly query for what you want from Oracle, rather than trying to replicate the data to Oracle. I tried doing this on Redhat 5.6, but I had issues with the ODBC driver that was written for Redhat 5.6. I later tries it with Redhat 6.3 and it worked much better. The issue dealt with how the ODBC driver read unicode characters. It is pretty easy to setup, you can install HAS as a different Oracle Home, or use the same Oracle home. Linux has a built in ODBC test program that will help you to get it working.

http://docs.oracle.com/cd/B28359_01/server.111/b28277/toc.htm