Also we could think of site domain based configuration variables. For example in "Configuration -> Website -> Output" section we could have dropdown (in blue bar on top) with all site domains listed and "Common" as first entry, like this:
- common
- domainA.com
- domainB.com
This way administrator could have any configuration variable to be domain-specific. When there is no value, then common value is used.
I see this as separate column with value in ConfigurationValues table, like we have for languages. For example:
- VariableValue
- sd1_VariableValue
- sd2_VariableValue
and so on.
We then will select values like this:
SELECT IF(sd2_VariableValue IS NULL, VariableValue, sd2_VariableValue)
FROM ConfigurationValues
WHERE VariableName = 'Site_Name';
Cases, when we deliberately want site domain configuration variable value to empty are not supported in this scheme.