Ok - your question is coming at the problem all wrong - at least from the perspective of Base.
First Base is not a database program, it is a tool for building front ends for a database. It has included, unfortunately, a customized version of HSQLdb which allows the database data to be embedded in an ODB (OpenDocument Database Document) file.
When you do this, embed the database in the document, there is no way to access the data from outside of LibreOffice - there is no JDBC or ODBC connector available.
Instead, given what you want to do, you would create your database using some real database package - that could be the standalone version of HSQLdb or SQLite(though it has some issues with Base) or MySQL or Postgres…etc. You would then connect the Base font end to the database and the Excel spreadsheet to the same database using VBA.