Question

I am working on a web application that store a lot of measurement data.

These measures have different types like temperature, flow, weight, concentration…

I am currently trying to implement a measurement units manager to let the users of the application choose which unit they want for each measure.

The data is in multiple tables :

Table1 : weightMeasure1 lengthMeasure1 TemperatureMeasure1

Table2 : weightMeasure2 lengthMeasure2 FlowMeasure2

Table3 : flowMeasure3

The users will be able to choose the unit that they want for each measure independently. So it will not be a metric/imperial choice.

All the data will be saved in there SI or SI derived unit in the Database. Because I am using PHP for my application I decided to use Zend_Measure to handle the conversion (after asking this question).

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How to define the unit of each measures in my database?

How to manage the user unit preferences?

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This is the best solution that I have so far :

I will create a property table :

property : property_id name column unit

• property_id is a unique incremented number (PK)
• name is a human readable name (optional)
• column is a concatenation of the table name and the column name (Unique constraint). For example : table2_lengthMeasure2
• unit is the Zend constant string defining the unit of the property in the database. For example : SQUARE_METER, KILOGRAM_PER_HOUR, … more details available in the Zend Framework API.

I will create a user_property_unit table to manage the user preferences :

user_property_unit : user_id property_id unit

• unit is the Zend constant string defining the unit of the property when it will be display in the UI for the user. For example it can be SQUARE_METER in the unit column of the property table and SQUARE_FOOT in the unit column of the user_property_unit

The problems that I see with this solution are:

• Using the concat of table name + column name seems not right to me…
• If I change the name of one of my columns it will not be reflected in the property table.

Thanks for your Help!!

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UPDATE
Is there any one why can help me even with some tips?

Answer 1

You want to have a separate table for PROPERTIES and a separate linking table TABLECOLUMNPROPERTY that makes a specific property the attribute of the column.

      PROPERTIES
      propid
      name
      unitid      FK references UNITS table


     TCP
     (tablename,columnname) composite PK
     propid


     UNITS
     unitid
     etc etc