best practice to store reference data as constant

I am a huge fan of storing such values in constants. My approach is:

- Each value is one constant

- To get a list of these, I create an expression returning a list of the constants in the desired order

I never had any issues with this approach. But, as soon as you need to allow the user to adjust values, like country codes or other semi-static things, a reference table in the DB can be the right solution.

First of all, you can try to keep the primary key of reference table data consistent across enviornment. This can be easily achieved by bit of discipline while developemnt and deployment process. Even then if you have doubt that Primary keys will not be consistent, you can have environment Specific constant so that values of these constants can be modified using properties file while deployment. 

I just use environment-specific constants for this.  It causes us no major problems.  I still remember trying to deal with this back before environment-specific constants were even an option - that could be a real nightmare.  In comparison, now it's a breeze.

In this case, I will utilize my own manually-created key value to reference the values.  I will still have a primary key on the table, but I don't care what it is unless I am grabbing it to update a value.  I maintain a 1-1 relationship of myKey to myValue manually. E.g.:

primaryKey (identity, auto-increment)
myKey (int)
myValue (string)

All code references values by myKey, deployments to new environments will insert/setup the data source as:

(primaryKey,myKey,myValue)
(null,1,Value1)
(null,2,Value2)
(null,3,Value3)

All code to reference the values utilizes the myKey column as the 'key'.  If I need to update this list programmatically, I will return the primaryKey at runtime based on the myKey value.