user: Question: What is the eccentricity when the semimajor axis is 20 AU?
Columns: ['Companion (in order from star)', 'Mass', 'Semimajor axis ( AU )', 'Orbital period ( s day )', 'Eccentricity', 'Inclination']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Asteroid belt', '3 AU', '3 AU', '3 AU', '3 AU', '—']
SQL:

assistant: SELECT "Eccentricity" FROM "Table" WHERE "Semimajor axis ( AU )" = '20 AU';