user: Question: when the nickname Halley is used, what are the date completed
Columns: ['PRINT NAME', 'NICKNAME', 'NUMBER OF COLORS', 'FRAMED SIZE', 'DATE COMPLETED']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['01474 Equalizer', 'N/A', 'Unknown', 'Unknown', 'Unknown']
SQL:

assistant: SELECT COUNT("DATE COMPLETED") FROM "Table" WHERE "NICKNAME" = 'Halley';