If you work primarily with Oracle databases, you may use SQL Developer. But you may also need to connect to Microsoft SQL Server databases and not necessarily want to install a new front-end database tool, such as Microsoft SQL Server Management Studio (SSMS). You can connect to SQL Server from SQL Developer.
First, download the appropriate JDBC Driver for the version of SQL Server that you need to connect to. Then follow the steps in the video at the link below on the Oracle website.
Good luck.
The Data Community 
appropriate driver being jTDS3.1 from Sourceforge – which will also give you connectivity to sybase ase
also note the feature support there is quite limited with an eye towards database migrations TO oracle database
Good luck, indeed 🙂
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