Purpose of LoweredUserName?

Question

What is the purpose of the LoweredUserName column in addition to the UserName column in the aspnet_Users table?

Answer 1

A case sensitive query is more case sensitive, more case insensitive.

Since the username is considered a natural key, many searches will be based on the username instead of the GUID (for example, logging).

The performance boost for small user tables will be negligible, but will be more noticeable as your user base grows.

Answer 2

I would suggest that these are more likely implementation details of the SqlServerMembershipProvider than some specific ASP.NET security practices. This probably affects the overall performance if you perform the LOWER operation once when the user is created, and then simply compare it with the parameter value. In this case, you will need to reduce only the value of the parameter.