Table: draft_history_52
Columns: round
pick
overall
name
position
college

Question: What is the maximum pick when WR was the position and Michigan the college, and the overall greater than 255?
SQL: SELECT MAX("pick") FROM draft_history_52 WHERE "position" = 'wr' AND "college" = 'michigan' AND "overall" > 255

Question: What is the total round when DB was the position, and the pick less than 21, and Jeff Welch as the name?
SQL: SELECT SUM("round") FROM draft_history_52 WHERE "position" = 'db' AND "name" = 'jeff welch' AND "pick" < 21