Name the parent unit for josef priller
CREATE TABLE "table1_28342423_1" (
  "parent_unit" text,
  "geschwader_base" text,
  "unit_gruppe_staffel" text,
  "aircraft_type" text,
  "commanding_officer" text
);
SELECT "parent_unit" FROM "table1_28342423_1" WHERE "commanding_officer"='Josef Priller';