user: Question: How many artists were there for the show Thoroughly Modern Millie?
Columns: ['Song title', 'Artist', 'Show', 'Difficulty', 'Effort', 'Year', 'Dancers']
Types: ['text', 'text', 'text', 'real', 'real', 'real', 'text']
Sample row: ['" All That Jazz "', 'Velma Kelly', 'Chicago', 1.0, 2.0, 1975.0, '♀/♀/♀/♀']
SQL:

assistant: SELECT COUNT("Artist") FROM "Table" WHERE "Show" = 'Thoroughly Modern Millie';