Support Microsoft SQL Server

[javrasya]

Description:

The way how django-river finds what is on approval is that it is using a library that is called django-cte which allows us to do some more advanced queries like windowing, joining two datasets, etc. It doesn't work with Microsoft SQL Database

Acceptance Criteria:

• Maybe implement a custom SQL scripts instead of using cte but to do the same thing. Different SQL script can be used with different DB drivers.