CODEWITHSUNDEEP
ruby-on-railsrubypostgresql
Gandalf StormCrow
Gandalf StormCrow

Reputation: 26192

Put unique constraint on multiple fields of a model

I'm working on a ruby on rails app and I want to put constraint on more than one field in database table i.e :

|id|field_one|field_two
 1  27        Value
 2  27        Value

This should be illegal because combination of field_one and field_two should not repeat. This below is perfectly fine :

|id|field_one|field_two
 1  27        Value
 2  28        Value
 3  27        AnotherValue

Can I make this constraints at database level? Or I need to do it in my ruby class level?

Upvotes: 2

Views: 126

Answers (2)

MrYoshiji
MrYoshiji

Reputation: 54882

Yes, you can do it with a regular validates, uniqueness and scope options:

validates :field_one, uniqueness: { scope: [:field_two] }

If you want your own custom validation method, you can do this:

validates :uniqueness_of_fields

private # optionnal
def uniqueness_of_fields
  if self.class.exists?(field_one: self[:field_one], field_two: self[:field_two])
    self.errors.add(:field_one, "Combination #{self[:field_one]} and #{self[:field_two]} already existings!"
    logger :do_your_thing # here is where you want to log stuff
    return false
  else
    return true # validation passes, is unique
  end
end

Upvotes: 3

Mori
Mori

Reputation: 27779

Yes, you can do this as a database constraint. In a migration:

add_index :table_name, [:column_name_a, :column_name_b], unique: true

Upvotes: 2

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