Question: What is the production code for the episode title "A Wrong Day's Journey into Right"?
SQL: SELECT "Production code" FROM "1-21312959-1" WHERE "Title" = '"A Wrong Day''s Journey into Right"';

Question: How many episodes had the us viewers (millions) figure of 5.0?
SQL: SELECT COUNT("No. in season") FROM "1-21312959-1" WHERE "US viewers (millions)" = '5.0';

Question: Who are the writers for the episode number in series 129?
SQL: SELECT "Written by" FROM "1-21312959-1" WHERE "No. in series" = 129.0;

Question: What is the us viewers (millions) figure for the episode titled "Witch Wars"?
SQL: SELECT "US viewers (millions)" FROM "1-21312959-1" WHERE "Title" = '"Witch Wars"';