I recently had the problem that a software upgrade that also involved a database upgrade did not work correctly and the database was "half" upgraded.

So I wanted to find out what data has changed in this half upgraded database. If you search the Internet, you will find many people recommending some third-party database comparison tools that cost money. But I was looking to find a legal free alternative.

Actually, there is one from Microsoft itself:

Go and download:

SQL Server Data Tools

https://docs.microsoft.com/en-us/sql/ssdt/download-sql-server-data-tools-ssdt

I have downloaded the ISO version that contains all modules. Then, install it and tick all the installation options. It even comes with a simple version of Visual Studio for free.

Once you start Visual Studio, go to:

Tools > SQL Server > New Data Comparison

You can then select the source and target database. Leave all the 4 boxes ticked. If you want to compare all the tables, just leave all boxes ticked on the next screen. Click Finish.

You will now see the changes to your database in bold.