user: Question: What is the highest In service for a vessel with a listed Unit of 12th Minesweeper Squadron?
Columns: ['Vessel', 'Origin', 'Type', 'In service', 'Unit']
Types: ['text', 'text', 'text', 'real', 'text']
Sample row: ['Xavery Czernicki Class', 'Poland', 'Logistic Support', 1.0, '2nd Minelaying and Transport Squadron']
SQL:

assistant: SELECT MAX("In service") FROM "Table" WHERE "Unit" = '12th Minesweeper Squadron';