user: Question: What episode number had production code E4423?
Columns: ['No. in series', 'No. in season', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (millions)']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [92.0, 1.0, '"Tragedy"', 'David Platt', 'Amanda Green', 'September 23, 2003', 'E4403', '13.23']
SQL:

assistant: SELECT "No. in season" FROM "Table" WHERE "Production code" = 'E4423';