When was the ship launched when the commissioned or completed(*) is 6 june 1864?
CREATE TABLE "ships" (
  "ship" text,
  "builder" text,
  "namesake" text,
  "renamed" text,
  "laid_down" real,
  "launched" text,
  "commissioned_or_completed" text
);
SELECT "launched" FROM "ships" WHERE "commissioned_or_completed"='6 June 1864';