Help with database schema
You could go with a more general structure, such as this:


appliances
----------
  id (PK)
  name (such as "bedroom TV", "main freezer", etc...)


parameter_types
---------------
  id (PK)
  type (such as "STRING", "INT", ...) - You might only be to enforce this in the application code, rather than in the database.


appliance_parameter
-------------------
  id (PK)
  name (such as "Model name", "Max. operating temperature", "IP address", etc...)
  parameter_type_id (FK to parameter_types.id)

appliance_parameter_values
--------------------------
  id
  appliance_id (FK to appliances.id)
  appliance_parameter_id (FK to appliance_parameters.id)
  value



This could be populated as:


appliances
ID  | name
----+------------
1   | Marcel's TV
2   | Main fridge
3   | coffee maker

parameter_types
ID  | type
----+---------
1   | STRING
2   | NUMERIC

appliance_parameter
ID  | name        | parameter_type_id
----+-------------+------------------
1   | model number| 1
2   | colour      | 1
3   | IP addr     | 1
4   | weight (kg) | 2

appliance_parameter_values
ID  | appliance_id  | appliance_parameter_id | value
----+---------------+------------------------+-------------
1   | 1             | 1                      | TV-01A
2   | 1             | 2                      | Magenta
3   | 1             | 3                      | 192.0.0.1
4   | 1             | 4                      | 3.2
5   | 3             | 3                      | 192.0.0.2
6   | 3             | 4                      | 1.2
7   | 3             | 2                      | grey
8   | 2             | 1                      | FRDG-001


In this example, you don't need to create specific columns for appliances. You create date for an appliance parameter in a specific table, then populate values into appliance_parameter_values when you need to. This system can handle any number of appliances with any number of parameters, as long as you can add the appropriate records for them.