How to make join queries using Sequelize on Node.js

Question

I am using sequelize ORM; everything is great and clean, but I had a problem when I use it with join queries. I have two models: users and posts.

Answer 1

In my case i did following thing. In the UserMaster userId is PK and in UserAccess userId is FK of UserMaster

UserAccess.belongsTo(UserMaster,{foreignKey: 'userId'});
UserMaster.hasMany(UserAccess,{foreignKey : 'userId'});
var userData = await UserMaster.findAll({include: [UserAccess]});

Answer 2

User.hasMany(Post, {foreignKey: 'user_id'})
Post.belongsTo(User, {foreignKey: 'user_id'})

Post.find({ where: { ...}, include: [User]})

Which will give you

SELECT
  `posts`.*,
  `users`.`username` AS `users.username`, `users`.`email` AS `users.email`,
  `users`.`password` AS `users.password`, `users`.`sex` AS `users.sex`,
  `users`.`day_birth` AS `users.day_birth`,
  `users`.`month_birth` AS `users.month_birth`,
  `users`.`year_birth` AS `users.year_birth`, `users`.`id` AS `users.id`,
  `users`.`createdAt` AS `users.createdAt`,
  `users`.`updatedAt` AS `users.updatedAt`
FROM `posts`
  LEFT OUTER JOIN `users` AS `users` ON `users`.`id` = `posts`.`user_id`;

The query above might look a bit complicated compared to what you posted, but what it does is basically just aliasing all columns of the users table to make sure they are placed into the correct model when returned and not mixed up with the posts model

Other than that you'll notice that it does a JOIN instead of selecting from two tables, but the result should be the same

Further reading:

• http://docs.sequelizejs.com/en/latest/docs/associations/#one-to-one-associations
• http://docs.sequelizejs.com/en/latest/docs/associations/#one-to-many-associations
• http://docs.sequelizejs.com/en/latest/docs/models-usage/#eager-loading

Answer 3

Model1.belongsTo(Model2, { as: 'alias' })

Model1.findAll({include: [{model: Model2  , as: 'alias'  }]},{raw: true}).success(onSuccess).error(onError);

Answer 4

While the accepted answer isn't technically wrong, it doesn't answer the original question nor the follow up question in the comments, which was what I came here looking for. But I figured it out, so here goes.

If you want to find all Posts that have Users (and only the ones that have users) where the SQL would look like this:

SELECT * FROM posts INNER JOIN users ON posts.user_id = users.id

Which is semantically the same thing as the OP's original SQL:

SELECT * FROM posts, users WHERE posts.user_id = users.id

then this is what you want:

Posts.findAll({
  include: [{
    model: User,
    required: true
   }]
}).then(posts => {
  /* ... */
});

Setting required to true is the key to producing an inner join. If you want a left outer join (where you get all Posts, regardless of whether there's a user linked) then change required to false, or leave it off since that's the default:

Posts.findAll({
  include: [{
    model: User,
//  required: false
   }]
}).then(posts => {
  /* ... */
});

If you want to find all Posts belonging to users whose birth year is in 1984, you'd want:

Posts.findAll({
  include: [{
    model: User,
    where: {year_birth: 1984}
   }]
}).then(posts => {
  /* ... */
});

Note that required is true by default as soon as you add a where clause in.

If you want all Posts, regardless of whether there's a user attached but if there is a user then only the ones born in 1984, then add the required field back in:

Posts.findAll({
  include: [{
    model: User,
    where: {year_birth: 1984}
    required: false,
   }]
}).then(posts => {
  /* ... */
});

If you want all Posts where the name is "Sunshine" and only if it belongs to a user that was born in 1984, you'd do this:

Posts.findAll({
  where: {name: "Sunshine"},
  include: [{
    model: User,
    where: {year_birth: 1984}
   }]
}).then(posts => {
  /* ... */
});

If you want all Posts where the name is "Sunshine" and only if it belongs to a user that was born in the same year that matches the post_year attribute on the post, you'd do this:

Posts.findAll({
  where: {name: "Sunshine"},
  include: [{
    model: User,
    where: ["year_birth = post_year"]
   }]
}).then(posts => {
  /* ... */
});

I know, it doesn't make sense that somebody would make a post the year they were born, but it's just an example - go with it. :)

I figured this out (mostly) from this doc:

• http://docs.sequelizejs.com/en/latest/docs/models-usage/#eager-loading