user: Question: What was the date of appointment when Jürgen Kohler was the outgoing manager?
Columns: ['Team', 'Outgoing manager', 'Manner of departure', 'Date of vacancy', 'Replaced by', 'Date of appointment']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['VfR Aalen', 'Edgar Schmitt', 'Sacked', '27 August 2008', 'Jürgen Kohler', '28 August 2008']
SQL:

assistant: SELECT "Date of appointment" FROM "Table" WHERE "Outgoing manager" = 'Jürgen Kohler';