Print the help for the delete command:
az sql db delete --help
You need to specify the database name, server name and Resource Group, e.g:
az sql db delete --name db01 --resource-group labs-sql --server <server-name>
You’ll be asked for confirmation.
When the command completes, browse to the SQL Server instance in the Portal and open the Deleted databases section.
You can restore a deleted database in the Portal, but it will take a few minutes before newly-deleted databases show up.
Deleting the Resource Group will delete the SQL Server:
az group delete -n labs-sql -y
That removes any databases and backups, and you can no longer restore deleted databases.