How do I perform joins using Knex in Node.js?

How do I perform joins using Knex in Node.js?

You can perform joins in Knex using the .join() method. For example, to join two tables, you can do something like this:

knex('users')
  .join('posts', 'users.id', '=', 'posts.user_id')
  .select('users.name', 'posts.title')
  .then(data => console.log(data));

What types of joins can I use with Knex?

Knex supports various types of joins, including inner joins, left joins, right joins, and full outer joins. You can specify the type of join like this:

knex('users')
  .leftJoin('posts', 'users.id', '=', 'posts.user_id')
  .select('users.name', 'posts.title');

Can I add conditions to my joins?

Yes, you can add conditions using the .on() method. For example:

knex('users')
  .join('posts', function() {
    this.on('users.id', '=', 'posts.user_id')
        .andOn('posts.published', '=', true);
  })
  .select('users.name', 'posts.title');

How do I handle multiple joins?

You can chain multiple .join() methods for multiple joins. For example:

knex('users')
  .join('posts', 'users.id', '=', 'posts.user_id')
  .join('comments', 'posts.id', '=', 'comments.post_id')
  .select('users.name', 'posts.title', 'comments.body');