Explanation
There are two administrative accounts (Server admin and Active Directory admin) that act as administrators.
One Azure Active Directory account, either an individual or security group account, can also be configured as an administrator. It is optional to configure an Azure AD administrator, but an Azure AD administrator must be configured if you want to use Azure AD accounts to connect to SQL Database.
References:
https://docs.microsoft.com/en-us/azure/sql-database/sql-database-manage-logins