user: Question: How many episodes had the production code 66210?
Columns: ['No. in series', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code']
Types: ['real', 'text', 'text', 'text', 'text', 'real']
Sample row: [2.0, '"Subterranean Homeboy Blues"', 'E.W. Swackhamer', 'Robert Palm', 'September20,1990', 66205.0]
SQL:

assistant: SELECT COUNT("No. in series") FROM "Table" WHERE "Production code" = 66210.0;