Can a database be in multiple availability groups?

Can a database belong to more than one availability group?

Databases may only belong to one availability group at a time. You can have more than one AlwaysOn Availability Group on your instance, but databases cannot belong to more than one group.

How many databases can you have in an availability group?

There is as such no limit defined. Microsoft has tested only upto 10 AG and 100 Databases. If you want to create more AGS, You will have to do so and test the workload you have to see that you do not land into performance issues for same.

How many availability groups can be created in SQL Server?

SQL Server 2017 introduced two different architectures for availability groups. Always On availability groups provide high availability, disaster recovery, and read-scale balancing. These availability groups require a cluster manager. In Windows, the failover clustering feature provides the cluster manager.

Can you write on a database that is a part of an always on availability group from the secondary replica?

Though you cannot write data to secondary databases, you can write to read-write databases on the server instance that hosts the secondary replica, including user databases and system databases such as tempdb.