Who were the previous champions from the event won on May 1, 2010?
CREATE TABLE "championships" (
  "championship" text,
  "current_champion_s" text,
  "previous_champion_s" text,
  "date_won" text,
  "location" text
);
SELECT "previous_champion_s" FROM "championships" WHERE "date_won"='may 1, 2010';