An Azure relational database service.
Hey,
External tables in synapse use Polybase feature to read files from blob whereas the external tables in Azure SQL are for elastic queries( to cross read data between databases) and not for reading a file.
But there are other ways like bulk insert, openrowset :
https://techcommunity.microsoft.com/t5/azure-sql-blog/loading-files-from-azure-blob-storage-into-azure-sql-database/ba-p/386133