user: Question: In what Round was a defensive tackle Pick # less than 19?
Columns: ['Round', 'Pick #', 'Overall', 'Name', 'Position', 'College']
Types: ['real', 'real', 'real', 'text', 'text', 'text']
Sample row: [1.0, 19.0, 19.0, 'Sean Weatherspoon', 'Linebacker', 'Missouri']
SQL:

assistant: SELECT "Round" FROM "Table" WHERE "Position" = 'defensive tackle' AND "Pick #" < 19.0;