user: Question: What is the pick number of the Defensive Back?
Columns: ['Overall Pick #', 'AFL Team', 'Player', 'Position', 'College']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [4.0, 'Miami Dolphins', 'Bob Griese', 'Quarterback', 'Purdue']
SQL:

assistant: SELECT "Overall Pick #" FROM "Table" WHERE "Position" = 'Defensive Back';