Python SQLite3 Pass Blob GUID from a Result to a Query

This is my first post on Stack Overflow, so apologies if I get anything wrong.

I'm fairly new to Python, and I have SQLite3 database which is created by an application I use, therefore I cannot alter the format of the db.

I have two tables, the main one which creates entries and assigns a unique ID in a column of data type GUID. This same GUID is then used in a second table to cross reference the item and store multiple additional entries.

What I need to do, is update one row of the main table, and then update any matching rows in the second table that have matching GUID's.

The problem is how can I pass the Blob value retrieved from the primary result into next query?

Thanks in advance.