user: Question: How many Picks have a Position of defensive back?
Columns: ['Round', 'Pick', 'Player', 'Position', 'School/Club Team']
Types: ['real', 'real', 'text', 'text', 'text']
Sample row: [1.0, 22.0, 'Ron Hallstrom', 'Guard', 'Iowa']
SQL:

assistant: SELECT COUNT("Pick") FROM "Table" WHERE "Position" = 'defensive back';