user: Question: How many different production codes are there for the episode with 4.69 million US viewers?
Columns: ['No. in series', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (millions)']
Types: ['real', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: [1.0, '" Pilot "', 'Michael Engler', 'Steve Franks', 'July7,2006', 1001.0, '6.06']
SQL:

assistant: SELECT COUNT("Production code") FROM "Table" WHERE "U.S. viewers (millions)" = '4.69';