Rake:db 迁移失败，预先存在的 mySQL 数据库

Question

我正在尝试使用预先存在的mySQL数据库创建一个rails实例，并且我正在遵循本指南。

步骤 1-3 有效，但在运行 rails 服务器时，它说有迁移挂起。

如果有人能告诉我错误源于何处，或者给出一些关于如何将预先存在的 mySQL 数据库与 rails 应用程序集成的一般指示，我将不胜感激。

运行 rake db：migrate 会产生此错误

== 1 CreateDatabase: migrating ================================================
-- create_table("Bill", {:primary_key=>"confirmationNo", :id=>:integer, :force=>:cascade, :options=>"ENGINE=InnoDB DEFAULT CHARSET=latin1"})
   -> 0.0556s
-- create_table("Customer", {:primary_key=>"creditCardNo", :id=>:integer, :force=>:cascade, :options=>"ENGINE=InnoDB DEFAULT CHARSET=latin1"})
rake aborted!
StandardError: An error has occurred, all later migrations canceled:
Mysql2::Error: Cannot delete or update a parent row: a foreign key constraint fails: DROP TABLE `Customer` CASCADE

这是我的schema.rb和migrate/001_create_database.rb

模式.rb

ActiveRecord::Schema.define(version: 0) do
  create_table "Bill", primary_key: "confirmationNo", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.integer "pointsEarned",            null: false
t.float   "amountDue",    limit: 24, null: false
  end
  create_table "Customer", primary_key: "creditCardNo", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.integer "guestID",             null: false
t.string  "username", limit: 30
t.string  "name",     limit: 30, null: false
t.index ["guestID", "username"], name: "guestID", unique: true, using: :btree
t.index ["username"], name: "username", using: :btree
  end
  create_table "Manager", primary_key: "managerID", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.string "name", limit: 10, null: false
  end
  create_table "Reservation", primary_key: "confirmationNo", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.date    "inDate"
t.date    "outDate"
t.boolean "availability", null: false
t.integer "roomNo"
t.integer "creditCardNo"
t.index ["creditCardNo"], name: "creditCardNo", using: :btree
t.index ["inDate", "outDate"], name: "inDate", using: :btree
t.index ["roomNo"], name: "roomNo", using: :btree
  end
  create_table "Room", primary_key: "roomNo", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.string "roomType", limit: 30, null: false
t.index ["roomType"], name: "roomType", using: :btree
  end
  create_table "Roomtype", primary_key: "roomType", id: :string, limit: 30, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.integer "capacity",            null: false
t.float   "rate",     limit: 24, null: false
  end
  create_table "Stay", primary_key: ["inDate", "outDate"], force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.date "inDate",  null: false
t.date "outDate", null: false
  end
  create_table "User", primary_key: "username", id: :string, limit: 1, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.integer "points", null: false
  end
  add_foreign_key "Bill", "Reservation", column: "confirmationNo", primary_key: "confirmationNo", name: "Bill_ibfk_1"
  add_foreign_key "Customer", "User", column: "username", primary_key: "username", name: "Customer_ibfk_1"
  add_foreign_key "Reservation", "Customer", column: "creditCardNo", primary_key: "creditCardNo", name: "Reservation_ibfk_3"
  add_foreign_key "Reservation", "Room", column: "roomNo", primary_key: "roomNo", name: "Reservation_ibfk_1"
  add_foreign_key "Reservation", "Stay", column: "inDate", primary_key: "inDate", name: "Reservation_ibfk_2", on_delete: :cascade
  add_foreign_key "Reservation", "Stay", column: "outDate", primary_key: "outDate", name: "Reservation_ibfk_2", on_delete: :cascade
  add_foreign_key "Room", "Roomtype", column: "roomType", primary_key: "roomType", name: "Room_ibfk_1"
end

迁移/001_create_database.rb

class CreateDatabase < ActiveRecord::Migration
  def self.up
ActiveRecord::Schema.define(version: 0) do
  create_table "Bill", primary_key: "confirmationNo", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.integer "pointsEarned",            null: false
t.float   "amountDue",    limit: 24, null: false
  end
  create_table "Customer", primary_key: "creditCardNo", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.integer "guestID",             null: false
t.string  "username", limit: 30
t.string  "name",     limit: 30, null: false
t.index ["guestID", "username"], name: "guestID", unique: true, using: :btree
t.index ["username"], name: "username", using: :btree
  end
  create_table "Manager", primary_key: "managerID", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.string "name", limit: 10, null: false
  end
  create_table "Reservation", primary_key: "confirmationNo", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.date    "inDate"
t.date    "outDate"
t.boolean "availability", null: false
t.integer "roomNo"
t.integer "creditCardNo"
t.index ["creditCardNo"], name: "creditCardNo", using: :btree
t.index ["inDate", "outDate"], name: "inDate", using: :btree
t.index ["roomNo"], name: "roomNo", using: :btree
  end
  create_table "Room", primary_key: "roomNo", id: :integer, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.string "roomType", limit: 30, null: false
t.index ["roomType"], name: "roomType", using: :btree
  end
  create_table "Roomtype", primary_key: "roomType", id: :string, limit: 30, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.integer "capacity",            null: false
t.float   "rate",     limit: 24, null: false
  end
  create_table "Stay", primary_key: ["inDate", "outDate"], force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.date "inDate",  null: false
t.date "outDate", null: false
  end
  create_table "User", primary_key: "username", id: :string, limit: 1, force: :cascade, options: "ENGINE=InnoDB DEFAULT CHARSET=latin1" do |t|
t.integer "points", null: false
  end
  add_foreign_key "Bill", "Reservation", column: "confirmationNo", primary_key: "confirmationNo", name: "Bill_ibfk_1"
  add_foreign_key "Customer", "User", column: "username", primary_key: "username", name: "Customer_ibfk_1"
  add_foreign_key "Reservation", "Customer", column: "creditCardNo", primary_key: "creditCardNo", name: "Reservation_ibfk_3"
  add_foreign_key "Reservation", "Room", column: "roomNo", primary_key: "roomNo", name: "Reservation_ibfk_1"
  add_foreign_key "Reservation", "Stay", column: "inDate", primary_key: "inDate", name: "Reservation_ibfk_2", on_delete: :cascade
  add_foreign_key "Reservation", "Stay", column: "outDate", primary_key: "outDate", name: "Reservation_ibfk_2", on_delete: :cascade
  add_foreign_key "Room", "Roomtype", column: "roomType", primary_key: "roomType", name: "Room_ibfk_1"
end
  end
  def self.down
# drop all the tables if you really need
# to support migration back to version 0
  end
end

干杯

Answer 1

你的MySQL数据库有"schema_migrations"表吗？Rails 依靠此表根据数据库和 schema.rb 文件中的版本号确定是否有任何待处理的迁移。更新 schema.rb 文件，使版本采用标准格式："20170326120700"而不是"0"，然后创建一个表"schema_migrations"，其中包含一个名为"version"的字段，并将版本号"20170326120700"插入到新表中。Rails 应该停止抱怨待处理的迁移。"版本"字段应为 VARCHAR(255( 类型。

要使 schema.rb 再次与数据库同步，您可以按照该过程重新创建 schema.rb，就像您在教程"rake db：schema：dump"中找到的那样。验证您的版本在 schema.rb 文件和"schema_migrations"表中是否仍然匹配。