Drizzle Team•2y ago

How to express "children" or "parent" relation with typescript?

Let's say I have a country and region tables. A region belongs to a country, so on the regiontable, there's a foreign key country_id to the country table. The question is if it is possible to have a Country type generated like this:

type Country {
  id: number;
}

type Region {
  id: number;
  country_id: number;
  country: Country; // This one is the difficult/impossible one to get? 
}

type Country {
  id: number;
}

type Region {
  id: number;
  country_id: number;
  country: Country; // This one is the difficult/impossible one to get? 
}

The goal is to be able to query a region and join it with the country table as well. Thank you!

9 Replies

Nelson SousaOP•2y ago

Current schema attempt:

export const countries = pgTable("country", {
  id: serial("id").primaryKey().notNull(),
  defaultName: varchar("default_name", { length: 50 }).notNull(),
});

export const regions = pgTable("region", {
  id: serial("id").primaryKey().notNull(),
  defaultName: varchar("default_name", { length: 50 }).notNull(),
  countryId: integer("country_id").references(() => countries.id),
});

export const countries = pgTable("country", {
  id: serial("id").primaryKey().notNull(),
  defaultName: varchar("default_name", { length: 50 }).notNull(),
});

export const regions = pgTable("region", {
  id: serial("id").primaryKey().notNull(),
  defaultName: varchar("default_name", { length: 50 }).notNull(),
  countryId: integer("country_id").references(() => countries.id),
});

Angelelz•2y ago

You could do that, but it's usually all the way around. I don't know what are you app requirements but this what people would typically do:

type Country = {
  id: number,
  defaultName: string,
  regions: Region[]
}
type Region = {
  id: number,
  defaultName: string,
  countryId: number
}

type Country = {
  id: number,
  defaultName: string,
  regions: Region[]
}
type Region = {
  id: number,
  defaultName: string,
  countryId: number
}

But you can make it however you want

Nelson SousaOP•2y ago

Sure. But how can I do it, either way? It is using the relations()?

Nelson SousaOP•2y ago

Angelelz•2y ago

The types you are looking for are not autimatically exported for you You either have to construct them manually or get them from the query you'd do for example

const countries = await db.query.countries.findFirst({
  with: { regions: true }
})

const countries = await db.query.countries.findFirst({
  with: { regions: true }
})

Will be the type you're looking for Or you can construct it like:

type Country = typeof countries.$inferSelect
type Region = typeof regions.$inferSelect
type RegionWithCountry = Region & { country: Country }

type Country = typeof countries.$inferSelect
type Region = typeof regions.$inferSelect
type RegionWithCountry = Region & { country: Country }

Nelson SousaOP•2y ago

I tried the first approach without success. Looks like I got a never type

Nelson SousaOP•2y ago

Is this expected?

Angelelz•2y ago

Nope, are you defining your relations the drizzle way? https://orm.drizzle.team/docs/rqb#declaring-relations

Drizzle Queries - DrizzleORM

Drizzle ORM | %s

Nelson SousaOP•2y ago

Checking 🔃 That was it, thank you!!

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How to express "children" or "parent" relation with typescript?

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