What is the total round when DB was the position, and the pick less than 21, and Jeff Welch as the name?
CREATE TABLE "washington_redskins_draft_history" (
  "round" real,
  "pick" real,
  "overall" real,
  "name" text,
  "position" text,
  "college" text
);
SELECT SUM("round") FROM "washington_redskins_draft_history" WHERE "position"='db' AND "name"='jeff welch' AND "pick"<21;