Using a Single Row configuration table in SQL Server database. Bad idea?

Question

In developing a shopping cart application I've found that I needed to save settings and configurations based on the administrator's preferences and requirements. This information can be anything from company information, Shipping account IDs, PayPal API keys, notification preferences, etc.

It seems highly inappropriate to create a table to store a single row in a relational database system.

What is the appropriate way to store this information?

Note: my DBMS is SQL Server 2008 and programming layer is implemented with ASP.NET (in C#).

Answer 1

I have done this two ways in the past - a single row table and a key/value pair table - and there are positives and negatives to each approach.

Single Row

• positive: the values are stored in the correct type
• positive: it is easier to deal with in code (due to the above)
• positive: default values can be given to each setting individually
• negative: a schema change is required to add a new setting
• negative: the table can become very wide if there are lots of settings

Key/Value Pair

• positive: adding new settings does not require a schema change
• positive: the table schema is narrow, with extra rows being used for new settings
• negative: each setting has the same default value (null/empty?)
• negative: everything has to be stored as strings (ie. nvarchar)
• negative: when dealing with the settings in code, you have to know what type a setting is and cast it

The single row option is by far the easiest one to work with. This is because you can store each setting in its correct type in the database and not have to store the types of the settings as well as their lookup keys in code.

One thing I was concerned with using this approach was having multiple rows in the "special" single row settings table. I overcame this by (in SQL Server):

• adding a new bit column with a default value of 0
• creating a check constraint to ensure that this column has a value of 0
• creating a unique constraint on the bit column

This means that only one row can exist in the table because the bit column has to have a value of 0, but there can only be one row with that value because of the unique constraint.