user: Question: What is the sum of NGC numbers for Constellation Vela?
Columns: ['NGC number', 'Object type', 'Constellation', 'Right ascension ( J2000 )', 'Declination ( J2000 )', 'Apparent magnitude']
Types: ['real', 'text', 'text', 'text', 'text', 'real']
Sample row: [3201.0, 'Globular cluster', 'Vela', '10h17m36.8s', '°24′40″', 9.2]
SQL:

assistant: SELECT SUM("NGC number") FROM "Table" WHERE "Constellation" = 'Vela';