CREATE TABLE table_204_26 (id DECIMAL, "name" TEXT, "position" TEXT, "birth date/age at start of campaign" TEXT, "games in campaign" TEXT, "club" TEXT)

which club was represented the most ?
SELECT "club" FROM table_204_26 GROUP BY "club" ORDER BY COUNT(*) DESC LIMIT 1
SELECT "club" FROM "table_204_26" GROUP BY "club" ORDER BY COUNT(*) DESC NULLS LAST LIMIT 1