title: design database relating to time attribute
body: <p>I want to design a database which is described as follows:
  Each product has only one status at one time point. However, the status of a product can change during its life time. How could I design the relationship between product and status which can easily be queried all product of a specific status at current time? In addition, could anyone please give me some in-depth details about design database which related to time duration as problem above? Thanks for any help</p>