Database design: how to store the voltage of the lamps?



  • The database stores information on lamps. Most lamps have a nominal voltage, but some have a permissible range.

    How is it better to keep voltage information on OBD and why?

    Screening options:

    • Two fields decimal (sighs)v_min, v_max) If the rated voltage is indicated, either keep the same values in both fields or leave one of the fields empty.
    • Two fields decimal♪ First at rated voltage, which also describes the mean voltage if there is a range. Second, under (max-min)/2 (percentage) null default).
    • One field varcharwhich stores either one digit or range
    • Create two daughter tables - one to the rated voltage, the other to the range.

    Any other options?



  • table (id int, 
           min int not null,  -- номинальное напряжение
           max int null       -- максимальное напряжение
          )
    

    Why is that? Imagine that in Table 1 billion of records, the lamps that can work with a certain voltage and return the sum (max - min) should be selected. If the data are stored in a varchar field, the lines will have to be converted into numbers when requested.




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