CREATE TABLE "house_of_oldenburg" (
  "birth" text,
  "marriage" text,
  "became_consort" text,
  "ceased_to_be_consort" text,
  "death" text,
  "spouse" text
);

Question: Name the became consort for marriage of 4 april 1721
SQL: SELECT "became_consort" FROM "house_of_oldenburg" WHERE "marriage"='4 april 1721';

Question: Name the birth of the person that has a spouse of frederick iv and became consort of 4 april 1721
SQL: SELECT "birth" FROM "house_of_oldenburg" WHERE "spouse"='frederick iv' AND "became_consort"='4 april 1721';

Question: Name the became consort for ceased to be consort of 4 april 1588 husband's death
SQL: SELECT "became_consort" FROM "house_of_oldenburg" WHERE "ceased_to_be_consort"='4 april 1588 husband''s death';

Question: Name the marriage of the person who is married for christian viii
SQL: SELECT "marriage" FROM "house_of_oldenburg" WHERE "spouse"='christian viii';