We are doing the Sitecore 10.2 upgrade. We have exported and restored the Collection Shard0 and Shard1 into our local. We have successfully executed our upgrade script.
I also faced the same issue while I uploaded the DB backup on Azure BlobStorage and tried to restore it directly via Portal.
Connect the Azure SQL Server to your local SSMS. For that, you need to add your IP address to the Azure SQL Server Firewall rule.
Once you are able to connect the Azure SQL server to the local SSMS then create the
BACPAC file of the database instead of
.bak file and try to restore the BACPAC file on Azure SQL Server.
See the blog post:
The easy way to do this is to make a copy of the Shard databases in the same Azure resource group or a different Azure resource group.
This approach is a lot quicker than exporting the database as a Copy of the database takes less than 10 minutes as against an Export of a few hours.
you can use the following command in Azure to copy the database
CREATE DATABASE [NewDatabaseName] AS COPY OF [ProdDatabaseServerName].[CurrentDatabaseName];
You can now update the database to 10.2 using the Sitecore scripts and rename the database using the following command
ALTER Database [UpdatedDatabase] MODIFY NAME = [ProdDatabaseName]
Or you can update connection strings to use the new database.
Please check my upgrade guide for 10.2 for more details
Hope this helps