user: Question: What is the engine code of the xDrive23d model?
Columns: ['Model', 'Years', 'Engine code', 'Power', 'Torque']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['sDrive16d', '2012-', 'N47D20', 'PS (kW; hp)@4000', 'N·m (lb·ft)@1750-3000']
SQL:

assistant: SELECT "Engine code" FROM "Table" WHERE "Model" = 'xDrive23d';