user: Question: How many years was louis armstrong performing?
Columns: ['Rank', 'Song title', 'Composer(s)', 'Performer(s)', 'Year']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [1.0, '" All I Want for Christmas Is You "', 'Mariah Carey and Walter Afanasieff', 'Mariah Carey', 1994.0]
SQL:

assistant: SELECT COUNT("Year") FROM "Table" WHERE "Performer(s)" = 'louis armstrong';