example many-to-many insert

[Deliana90]

How to do create Post and CategoriesOnPosts in edgedb? can you give example using typescript please, thanks.

[raddevon]

I'll start with the schema:

module default {
  type Post {
    required property title -> str;
    multi link categories -> Category;
  }
  type Category {
    required property name -> str;
  }
}

A couple of notes on the schema as compared to that in the Prisma example:

• You don't need to create the IDs. EdgeDB handles that for you.
• You don't need the intermediary table which is CategoriesOnPosts in this example.

With that schema, you can insert a post with new categories using this code in TypeScript:

const client = createClient();
const insertPostQuery = e.insert(e.Post, {
  title: "How to be Bob",
  categories: e.set(
    e.insert(e.Category, { name: "Category 1" }),
    e.insert(e.Category, { name: "Category 2" })
  ),
});
await insertPostQuery.run(client);

That's what you'd do if you needed to insert new categories. If Category 1 and Category 2 already exist, you could do this instead:

const client = createClient();
const insertPostQuery = e.insert(e.Post, {
  title: "How to be Bob Part 2",
  categories: e.set(
    e.select(e.Category, () => ({ filter_single: { name: "Category 1" } })),
    e.select(e.Category, () => ({ filter_single: { name: "Category 2" } }))
  ),
});
await insertPostQuery.run(client);

If you have existing categories and know the IDs of those categories rather than the names, you could do this instead:

const client = createClient();
const insertPostQuery = e.insert(e.Post, {
  title: "How to be Bob Part 2",
  categories: e.set(
    e.select(e.Category, () => ({ filter_single: { id: "<category-1-id>" } })),
    e.select(e.Category, () => ({ filter_single: { id: "<category-2-id>" } }))
  ),
});
await insertPostQuery.run(client);

replacing <category-1-id> and <category-2-id> with those actual IDs.

If you don't know whether the categories exist, you could do this:

const client = createClient();
const insertPostQuery = e.insert(e.Post, {
  title: "How to be Bob Part 2",
  categories: e.set(
    e.insert(e.Category, { name: "Category 1" }).unlessConflict((category) => ({on: category.name, else: category})),
    e.insert(e.Category, { name: "Category 2" }).unlessConflict((category) => ({on: category.name, else: category})),
  ),
});
await insertPostQuery.run(client);

Note that, as @Syzuna noted in their reply, unlessConflict would required you change the schema to make the category name exclusive. That would look like this:

module default {
  type Post {
    required property title -> str;
    multi link categories -> Category;
  }
  type Category {
    required property name -> str {
      constraint exclusive;
    }
  }
}

I hope this helps!

[Syzuna]

Wouldn't you need to adjust your schema for the last example? More specifically add an unique constraint on the name for unless conflict to work?

[raddevon]

@Syzuna Yes, you're right. Good catch! I'll edit the reply and make note of that.