user: Question: What is every director with production code of NABF13?
Columns: ['№', '#', '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: [465.0, 1.0, '" Elementary School Musical "', 'Mark Kirkland', 'Tim Long', 'September26,2010', 'MABF21', '7.75']
SQL:

assistant: SELECT "Directed by" FROM "Table" WHERE "Production code" = 'NABF13';