I notice that Database Diagrams are not supported in SSMS version 18, any idea why, and is there a way to get the same functionality?
And why is the T-SQL debugger gone now?
As it was posted at June 11, 2019, to announce that SQL Server Management Studio (SSMS) 18.1 is now generally available, the Database diagrams is back in SSMS 18.1 along side SSBDIAGNOSE.EXE and Integration Services (SSIS)
Original Answer:
The feature is deprecated, you can visit SQL Server Management Studio - Changelog (SSMS) page and read the Deprecated Features in SSMS 18.0.
Deprecated Features
The following features are no longer available in SSMS:
- T-SQL Debugger
- Database Diagrams
- …
Those features are available in earlier versions, you can use one of them a long side with SSMS 18.0
SQL Server Management Studio 18.1 was just released on June 11th, and it supports Database Diagrams again.
According to this blogpost SQL Server Management Studio (SSMS) 18.1 is now generally available:
Yes, we’ve heard the feedback; Database Diagrams is back.
Here's the SSMS download page.
I had the same problem with SSMS 18 (preview 4)
To get the functionality, install a previous SSMS release until the fix comes.
来源：https://stackoverflow.com/questions/52525336/ssms-version-18-no-database-diagrams