How to make join queries using Sequelize on Node.js

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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

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