Database Normalization with user input - mysql

Question

I develop a mysql database that will contain the country,city and occupation of each user.
While I can use a "country" table and then insert the id of the country into the user table, I still have to look for the perfect method for the other two tables.
The problem is that the city and occupation of each user are taken from an input field, meaning that users can type "NYC" or "New York" or "New York City" and millions of other combinations for each town, for example.
Is it a good idea to disregard this issue, create an own "town" table containing all the towns inserted by users and then put the id of the town entry into the user table or would it be more appropriate to use a VARCHAR column "town" in the user table and not normalize the database concerning this relation?
I want to display the data from the three tables on user profile pages.
I am concerned about normalization because I don't want to have too much redundant data in my database because it consumes a lot of space and the queries will be slower if I use a varchar index instead of an integer index for example (as far as I know):
Thanks

Answer 1

We had this problem. Our solution was to collect the various synonyms and typo-containing versions that people use and explicitly map them to a known canonical city name. This allowed to correctly guess the name from user input in 99% of cases.
For the remaining 1%, we created a new city entry and marked it as a non-canonical. Periodically we looked through non-canonical entries. For recognizable known cities, we remapped the non-canonical entry to the canonical (updating FKs of linked records and adding a synonym). For a genuinely new city name we didn't know about we kept the created entry as canonical.
So we had something like this:
table city(
id integer primary key,
name varchar not null, -- the canonical name
...
);
table city_synonym(
name varchar primary key, -- we want unique index
city_id integer foreign key references(city.id)
);

Answer 2

Usually data normalization helps you to work with data and keep it simple. If normalized schema not fit your needs you can use denormalized data as well. So it depends on queries you want to use.
There is no good solution to group cities without creating separate table where you will keep all names for each city within single id. So it will be good to have 3 tables then: user(user_id, city_id), city (city_id, correct name), city_alias(alias_id, city_id, name).

Answer 3

It would be better to store the data in a normalized design, containing the actual, government recognized city names.
#Varela's suggestion of an 'alias' for the city would probably work well in this situation. But you have to return a message along the lines of "You typed in 'Now Yerk'. Did you perhaps mean 'New York'?". Actually, you want to get these kinds of corrections regardless...
Of course, what you should probably actually store isn't the city, but the postal/zip code. Table design is along these lines:
State:
Id State
============
AL Alabama
NY New York
City:
Id State_Id City
========================
1 NY New York
2 NY Buffalo
Zip_Code:
Id Code City_Id
=========================
1 00001-0001 1
And then store a reference to Zip_Code.Id whenever you have an address. You want to know exactly which zip code a user has (claimed) to be a part of. Reasons include:
Taxes for retail (regardless of how Amazon plays out).
Addresses for delivery (There is a Bellevue in both Washington and New York, for example. Zip codes are different).
Social mapping. If you store it as 'user input' cities, you will not be able to (easily) analyze the data to find out things like which users live near each other, much less in the same city.
There are a number of other things that can be done about address verification, including geo-location, but this is a basic design that should help you in most of your needs (and prevent most of the possible 'invalid' anomalies).