What is the sum of the game with a PWin% of —, Term [c] of 1987–1988, and Win% less than 0.506?
CREATE TABLE "coaches" (
  "name_b" text,
  "term_c" text,
  "games" real,
  "winpct" real,
  "p_winpct" text
);
SELECT SUM("games") FROM "coaches" WHERE "p_winpct"='—' AND "term_c"='1987–1988' AND "winpct"<0.506;