Question

How can I add a unique, auto-incrementing primary key (IdCustomer) in Rails? And what about if I have more than one key?

class CreateCustomers < ActiveRecord::Migration
  def change
    create_table :customers do |t|
      t.integer :IdCustomer
      t.string :Login
      t.string :Password
      t.string :Email
      t.string :Skype
      t.integer :ICQ
      t.string :Firstname
      t.string :Lastname
      t.string :Country
      t.string :State
      t.string :City
      t.string :Street
      t.string :Building
      t.integer :Room
      t.string :AddressNote
      t.date :DateOfReg
      t.integer :CustGroup
      t.float :TotalBuy

      t.timestamps
    end
  end
end

Help me with this, please, get it on my code. Becouse now i get

rake aborted! An error has occurred, all later migrations canceled:

Mysql2::Error: Incorrect table definition; there can be only one auto
column and it must be defined as a key: CREATE TABLE credit_cards
(id int(11) DEFAULT NULL auto_increment PRIMARY KEY, IdCustomer
int(11), IdCard int(11) DEFAULT NULL auto_increment PRIMARY KEY,
Number varchar(255), NameOfCard int(11), ExpiryDate date,
created_at datetime NOT NULL, updated_at datetime NOT NULL)
ENGINE=InnoDB

Answer 1

You cannot set more than 1 column auto_increment. Delete auto_increment PRIMARY KEY after IdCard int(11) DEFAULT NULL and put UNIQUE instead if you want to make that column unique