html - 如何在 Ruby on Rails 5 中使用起始值自动增加自定义 ID？

Question

我正在进行迁移，我删除了每个表的默认 'id'。我创建了一个特殊字段而不是 'student_id'，我想让它从 1001 开始自动递增。

这是我的代码:

class CreateStudents < ActiveRecord::Migration[5.0]
  def up
    create_table :students, :id => false do |t|
      t.integer "student_id"
      t.string "first_name", :limit => 25
      t.string "last_name", :limit => 50
      t.string "email", :default => ' ', :null => false
      t.string "birthday"
      t.string "subjects"
      t.string "teachers"
      t.string "username", :limit => 25
      t.string "password_digest", :limit => 40
      t.timestamps
    end
    execute "CREATE SEQUENCE students_student_id_seq OWNED BY students.student_id INCREMENT BY 1 START WITH 1001"
  end

  def down
  drop_table :students
  execute "DELETE SEQUENCE students_student_id_seq"
  end

end

我得到了 ff 错误:

Mysql2::Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'SEQUENCE students_student_id_seq OWNED BY students.student_id INCREMENT BY 1 STA' at line 1

如何在 Ruby on Rails 5 中使用起始值自动增加自定义 ID？

Answer 1

execute "CREATE SEQUENCE students_student_id_seq OWNED BY students.student_id INCREMENT BY 1 START WITH 1001"

上面是Postgresql语法，你的数据库好像是MySQL。

无论如何，您可以通过将student_id设置为主键，然后更新增量起始值来实现您想要的。

def change
  create_table :students, :id => false do |t|
    t.integer "student_id", primary_key: true
    t.string "first_name", :limit => 25
    t.string "last_name", :limit => 50
    t.string "email", :default => ' ', :null => false
    t.string "birthday"
    t.string "subjects"
    t.string "teachers"
    t.string "username", :limit => 25
    t.string "password_digest", :limit => 40
    t.timestamps
  end

  reversible do |dir|
    dir.up { execute "ALTER TABLE students AUTO_INCREMENT = 1000" }
  end
end