Question

I have a table that stores a person’s information with close to 10 million rows.

Currently State is a char(2) field on the person table. This leads to tons of duplication of data as you would expect. If I normalize State data into it’s own table and create an FK to it in the person table would this result in faster query times?

Before:

SELECT Name, City, State FROM Person WHERE State = 'WI'

After:

SELECT p.Name, p.City, s.Name as State
FROM Person p
    INNER JOIN State s ON p.State == s.Id
WHERE s.Name = 'WI'

It seems to me that this would accomplish an increase in performance but I am far from an expert when it comes to optimizing queries.

Answer 1

Normalization can result in decreased performance, but rarely if ever will it increase your performance in a case like this, because now the server has to look at two places on disk instead of just one.

Normalization has two purposes:

1. Reduce the amount of data stored on the disk
2. Allow data to be updated in a single place

Your query will not benefit from either of these advantages as

1. there is not much of a difference between a char(2) and an int (the foreign key)
2. the two digit code for a state will never change, so you will never need to update it