Sequelize use camel case in JS but underscores in table names

Not directly in your column definition, but you could take a look at getters and setters:

http://sequelizejs.com/documentation#models-getters---setters-defining-as-part-of-the-model-options

Although this options requires you to define a getter and setter for each column manually, it cannot be automated. Furthermore, both your getters and the actual column names will then be available on the object.

I think there is an issue for this functionality on github, but I cannot find it right now

---

actual link https://sequelize.org/master/manual/models-definition.html#getters--amp--setters

You can achieve this for both models (tables) and keys (fields) using a newer version of Sequelize.

I am using 4.29.2 and my models looks like this:

const Post = sequelize.define('post', {
    id: {
      type: DataTypes.UUID,
      defaultValue: DataTypes.UUIDV4,
      primaryKey: true,
      allowNull: false,
    },
    isActive: {
      type: DataTypes.BOOLEAN,
      defaultValue: true,
      allowNull: false,
      field: 'is_active',
    },
    isDeleted: {
      type: DataTypes.BOOLEAN,
      defaultValue: false,
      allowNull: false,
      field: 'is_deleted',
    },
  }, {
    indexes: [
      {
        unique: false,
        fields: ['is_active'],
      },
      {
        unique: false,
        fields: ['is_deleted'],
      },
    ],
    defaultScope: {
      where: {
        isActive: true,
        isDeleted: false,
      },
    },
  });

const PostComments = sequelize.define('postComments', {
    id: {
      type: DataTypes.UUID,
      defaultValue: DataTypes.UUIDV4,
      primaryKey: true,
      allowNull: false,
    },
    postId: {
      type: DataTypes.UUID,
      allowNull: false,
      field: 'post_id',
    },
    comment: {
      type: DataTypes.STRING,
      allowNull: false,
    },
  }, {
    tableName: 'post_comments',
    indexes: [
      {
        unique: false,
        fields: ['post_id'],
      },
    ],
  });


  Post.hasMany(PostComments, {
    foreignKey: 'postId',
    constraints: true,
    as: 'comments',
  });

  PostComments.belongsTo(Post, {
    foreignKey: 'postId',
    constraints: true,
    as: 'post',
  });

As you can see, I'm setting the tableName value for models (tables) and field values for keys (fields).

When I run:

sequelize.query('SET FOREIGN_KEY_CHECKS = 0', { raw: true })
  .then(() => {
    conn.sync({ force: true }).then(() => {
      console.log('DONE');
    });
  });

The result is:

Executing (default): SET FOREIGN_KEY_CHECKS = 0
Executing (default): DROP TABLE IF EXISTS `post_comments`;
Executing (default): DROP TABLE IF EXISTS `post`;
Executing (default): CREATE TABLE IF NOT EXISTS `post` (`id` CHAR(36) BINARY NOT NULL , `is_active` TINYINT(1) NOT NULL DEFAULT true, `is_deleted` TINYINT(1) NOT NULL DEFAULT false, `created_at` DATETIME NOT NULL, `updated_at` DATETIME NOT NULL, PRIMARY KEY (`id`) ENGINE=InnoDB;
Executing (default): CREATE TABLE IF NOT EXISTS `post_comments` (`id` CHAR(36) BINARY NOT NULL , `post_id` CHAR(36) BINARY NOT NULL, `comment` VARCHAR(255) NOT NULL, `created_at` DATETIME NOT NULL, `updated_at` DATETIME NOT NULL, PRIMARY KEY (`id`), FOREIGN KEY (`post_id`) REFERENCES `post` (`id`) ON DELETE CASCADE ON UPDATE CASCADE) ENGINE=InnoDB;

For anyone finding this later on it's now possible to explicitely define what the database field should be named:

var User = sequelize.define('user', {
  isAdmin: {
    type: DataTypes.BOOLEAN,
    field: 'is_admin'
  }
});

2019+

In Sequelize v5 you can now use the underscored: true attribute

---

const User = sequelize.define('User', {
    username: DataTypes.STRING,
    password: DataTypes.STRING
  }, {underscored: true});

https://sequelize.org/master/class/lib/model.js~Model.html#static-method-init