How many years Joined have a Size smaller than 417, and an IHSAA Class of A, and a School of jac-cen-del?
CREATE TABLE "membership" (
  "school" text,
  "location" text,
  "mascot" text,
  "size" real,
  "ihsaa_class" text,
  "county" text,
  "year_joined" real,
  "previous_conference" text
);
SELECT COUNT("year_joined") FROM "membership" WHERE "size"<417 AND "ihsaa_class"='a' AND "school"='jac-cen-del';