Copying a table in SQL Server database to Oracle database
this can be done if you are using SQL Server Management Studio. The method is as follows:-

Goto the source schema on SQL Server

Right click > Export data

Select source as current schema

Select destination as "Oracle OLE provider"

Select properties, then add the service name into the first box, then username and 
password, be sure to click "remember password"

Enter query to get desired results to be migrated

Enter table name, then click the "Edit" button

Alter mappings, change nvarchars to varchar2, and INTEGER to NUMBER

Run

Repeat process for remaining tables, save as jobs if you need to do this again in the future