user: Question: What period were conscituency contested is Aljunied GRC?
Columns: ['Parliament', 'Name', 'Period in office', 'Birth and death years', 'General election contested', 'Constituency contested', 'Political party']
Types: ['text', 'text', 'text', 'text', 'real', 'text', 'text']
Sample row: ['7th', 'Lee Siew-Choh', '16 December1989– 31 August 1991', '1917–2002', 1988.0, 'Eunos GRC', "Workers' Party"]
SQL:

assistant: SELECT "Period in office" FROM "Table" WHERE "Constituency contested" = 'Aljunied GRC';