如何在Ruby on Rails 5中以起始值自动递增自定义ID？

用户名

大家好，我正在进行迁移，因此我删除了'id'每个表的默认设置。我创建了一个特殊字段，'student_id'并希望使其从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

我收到了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中自动使用起始值自定义id增量？

米海·丁库列斯库（Mihai Dinculescu）

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

上面是Postgresql语法，您的数据库似乎是MySQL。

无论如何，您可以通过设置student_id为主键并更新增量起始值来实现所需的功能。

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

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