Question

I have to create a database that will store a huge amount of people along with their addresses, that will have to be searchable by place (i.e. find people in that or other city).

I am doubting whether I should keep the city field in the address as simple varchar or create a city table and refer to it, to avoid duplicate city names etc.

Note: I am using SQL-Server and will access the data via EF.

Answer 1

Background

Authority table – a reference table that contains the possible values for the “thing” for which it is an authority. For example, a Country authority table would contain all possible values for country.

An Answer

Depending on your definition of “huge amount …” you definately will want to have some authority tables.
Based on the geographic range of your addresses, some or all of these seem like a good start for your authority tables:

1. Country – if you allow addresses in more than 1 country, it seems like a good thing to have as an authority table
2. State (or province) – nations are broken into provences and/or states. These are a good candidate for an authority table.
3. City – cities are (mostly) fixed entities that have a defined name. Another candidate for an anthority table. This should include towns, villages, cities, and other (rural residents may not live in a city, village, town, or anything else).
4. Street Name – streets have names (or numbers) that are (mostly) fixed. This is a candidate for an authority table. Street name will depend on a combination of city, state, and country to make it unique. For example City “Blah” may have a street named “Mainne” while city “NotBlah: may not have a street named “Mainne”
5. Postal Code (zip code in the USA) is a likely candidate for an authority table. For example, there is no zip code 00001 in the USA.