text: SELECT CONCAT(m.FirstName, ' ', m.LastName) AS [Mechanic], 
  	   AVG(DATEDIFF(DAY, j.IssueDate, j.FinishDate)) AS [Average Days]  
    FROM Jobs AS j
  JOIN Mechanics AS m ON m.MechanicId = j.MechanicId
  GROUP BY m.FirstName, m.LastName, m.MechanicId
  ORDER BY m.MechanicId