what database field type should i use ??

in a database table if there is a field which has a certain set of fixed values. for example staus => {Single, Married, Divorced } OR state => {California, Albama, Olaska ...}

so what should be preferred way out of the following for storing the values

1. Keep the field as "string(Rails)" VARCHAR(MySQL) itself ....and while showing the field just show the field value.

2. Keep the field internally as a code like {:california => 01, :albama => 02, washington => 03 ....} but while showing the state show only the corresponding state.

By using option 2, a certain disadvantage is extra computation time required to find out corresponding state name based on code when showing the state field to user. But an advantage could be in terms of smaller database. In my opinion, saving 01 as an integer could save significant space than storing "california" if number of records happen to be in tens of thousands .

please suggest ??

vipin

In the case of method 2 where would you store the tens of thousands of strings if not in the database? Colin

Vipin wrote:

in a database table if there is a field which has a certain set of fixed values. for example staus => {Single, Married, Divorced } OR state => {California, Albama, Olaska ...}

so what should be preferred way out of the following for storing the values

I use ENUM() columns in mysql - rails treats them as strings so everything works (apart from schema dumps)

just realize...

in the case od 1st method: everything is simple, but db grows.. but... you made some typo mistake (eg Albama instead of Alabama) and what then.. repair entire table to get the correct results? weird

2nd method: I'm using it for a small enumeration lists (not hundreds/thousands items - then is better to use db enumeratin methods, like countries table and country_id column)

in app/model/some_model.rb

@@enum_list = %w( value1 value2 value3 )

# to use in erb templates for form.select() helper def self.enum_list_for_select    @@enum_list.enum_with_index.collect{|k,v| [k,v]} end

def enum_list_to_text    self.enum_list.nil? ? 'undefined' : @@enum_list[self.enum_list] end

tom

Vipin wrote:

Vipin wrote:

in a database table if there is a field which has a certain set of

fixed values. for example

staus => {Single, Married, Divorced }

OR

state => {California, Albama, Olaska …}

so what should be preferred way out of the following for storing the

values

I use ENUM() columns in mysql - rails treats them as strings so

everything works (apart from schema dumps)

Sorry, I misunderstood the question, I assumed you wanted to know how to store the country names in a countries table. I did not realise that in option 1 you meant storing the string in every record that references country, though that is what you said, I did not read it carefully. Now that I understand, I would suggest some variant of option 2, store an id in each record referencing a country and determine the string by an enumeration or table lookup later. Worrying too much about computing time during development is a mugs game, an application always ends up with most of its computing time in an area you do not expect. Worry about optimisation later when (or more likely if) a particular area becomes a problem.

Colin

Sometimes it''s a matter of taste or design constraint, but why not use a small join table and a foreign key? ENUM is also a great choice, as these guys have pointed out, but sometimes there is a bit of overhead -- but you shouldn't worry about that until it becomes an issue. Personally, I find it easier to maintain a simple join table and FK relationships than to mess with ENUM field types.

I don't know if this is still applicable, but it seems like there is a bit of data massaging in Rails for the ENUM type (Rails converts it internally to VARCHAR):

http://lists.rubyonrails.org/pipermail/rails/2005-January/001536.html

I like to let the database do as much work as it can, :slight_smile:

HTH!

Billee D.

It's about performance.

if you'll have marriage status (single/married/divorced/etc) in table marriagestatuses, and using belongs_to/has_many via marriagestatus_id, and not using :include => marriagestatuses in you 'queries', db will do a lot of queries just for a few enumerables.

so each of us have to decide whether to use another 'enumerate table' or nor

tom

Billee D. wrote:

in database only ...i am going to store both string /id in database only

Thanks ! i will try this.

Colin, yes i guess 2nd variant will be better. thanks

But Bilee, if we use another table and do the mapping through foreign key won;t it be even poorer as we will be making 2 SQL queries to access the same record. which we are doing in one SQL query in above two methods.

But i ll certainly check the link provided.

vipin

I would also use a small join table with your sets ... so your users can add properties on the fly.

The question isn't really a performance issue, but rather one of customization. If users are likely to need to add values to an enumeration, (example: category for a blog post), then a lookup table is a good idea. If the values are substantially unlikely to change (see your examples - marriage status and state) then there's not a lot to be gained by complicating the DB.

--Matt Jones

Though you might already have solved your issue at hand, I've recently ran into a similar situation and written a small plugin for it, columns are backed by integers, but in ruby you can treat them using symbols or whatever:

class User < ActiveRecord::Base   as_enum :status, { :single => 0, :married => 1, :divorced => 2 } end

Then create an integer column:

add_column :users, :status_cd, :integer

It's then possible to easily access these values using @user.status:

@user = User.new @user.status = :married # => implies @user.status_cd = 1

For my problem I also required some shorthands to check for values, so I've added also <symbol>? methods:

@user.married? # => true @user.single? # => false

The code lives at github http://github.com/lwe/simple_enum/tree/master any feedback is appreciated

cheers, lukas