Re: Three tables or one?
table devicetypes
~~~~~~~~~~~~~~~~~
typeid primary key
typename
Values
~~~~~~
1, "Phone"
2, "SatNav"
table parameters
~~~~~~~~~~~~~~~~
paramid primary key
paramname
Values
~~~~~~
1, "GPRS"
2, "802.11g"
3, "HSPDA"
table devices
~~~~~~~~~~~~~
deviceid primary key
typeid references devicetypes (typeid)
Values
~~~~~~
1, 1 -- Phone
2, 2 -- SatNav
3, 1 -- Phone
4, 1 -- Phone
table device_parameters
~~~~~~~~~~~~~~~~~~~~~~~
devpramid primary key
deviceid references devices (deviceid)
paramid references parameters (paramid)
value
Values
~~~~~~
1, 1, 1, "11GHz" -- Phone, GPRS
2, 3, 2, "Channel 6" -- Phone, 802.11g
3, 2, 3, "Unknown" -- SatNav, HSPDA
So basically you have a look up table for device types and valid parameter names.
You then create a device of a particular type.
The last table is a list of all of the parameters that you have set for a particular device.
You can create views to link the tables together and get the device type and it's parameters etc.
HTH.
James.