True ETL Tools
If you need more than just to copy data from MariaDB to Google Cloud SQL for SQL Server, you may use Skyvia's powerful ETL functionality for MariaDB and Google Cloud SQL for SQL Server integration. Skyvia's Import tool will correctly extract MariaDB data, transform it, and load to Google Cloud SQL for SQL Server when Google Cloud SQL for SQL Server tables have different structure than MariaDB tables. Moreover, Skyvia Import allows loading data in any direction, supporting Reverse ETL scenario.
For more complex cases, you can use Data Flow and Control Flow tools. They are designer-based solutions for creating complex data pipelines, involving not only MariaDB and Google Cloud SQL for SQL Server connectors, but any number of connectors in one integration. With these tools you can automate data workflows, involving custom logic, complex multistage transformations, combine data from different sources, load them into multiple destinations at once and many more.