How many "account representatives" are there in Chicago with a good performance?
account representatives is a position title; Chicago refers to locationcity = 'Chicago'; good performance refers to performance = 'Good'
SELECT COUNT(*) FROM employee AS T1  INNER JOIN location AS T2  ON T1.locationID = T2.locationID INNER JOIN position AS T3  ON T3.positionID = T1.positionID WHERE T3.positiontitle = 'Account Representative' AND T2.locationcity = 'Chicago' AND T1.performance = 'Good'