Ms sql server - database / schema / tablename

[Irupt]

Good morning,
I work with Sql server on several databases. When I do a select it is common for me to join tables between several databases. Is there a way on Kysely to specify the database/schema/tablename?

Ex:
Select * from dbname1.dbo.tablename1 T1 inner join dbname2.dbo.tablename2 T2 on T1.ID = T2.ID

tyvm

[koskimas]

Yes. See this recipe https://kysely.dev/docs/recipes/schemas

[Irupt]

Thanks, but unfortunately it only works with a schema but not with a database.schema

[koskimas]

Oh, that's true. I'm not sure if we can make that work without complicating everything too much. But let's take a look. For now it's impossible to do this without using raw SQL.

// PersonTable is the table interface.
.selectFrom(sql<PersonTable>`foo.bar.baz.person`.as('person'))

or something like:

function table<T>(...t: string[]) {
  return sql<T>`${sql.id(...t)}`
}

...

.selectFrom(table<PersonTable>("foo", "bar", "baz", "spam").as('person'))

[gittgott]

Just want to add this here:

With some slight modifications, the solution above covers all of my needs for cross database joins.

I have a bunch of databases that I do not have much control over and it's structured such that there are a few situations in which I need to join two tables across databases. I also have kysely-codegen writing all of my database schemas out to separate TypeScript files. I have some custom codegen alongside that which will create a TypeScript type that includes all of the databases from my server like so in file called schemas/index.ts:

import { DB as DB1 } from "./db1";
import { DB as DB2 } from "./db2";

export type Server = {
  DB1: DB1;
  DB2: DB2;
};

where ./db1 is something like

export interface DB {
  person: {
    id: Generated<string>
    first_name: string
    last_name: string | null
    created_at: Generated<Date>
    age: number
  }
}

and ./db2 is something like

export interface DB {
  pet: {
    id: Generated<string>
    name: string
    owner_id: string
    species: 'cat' | 'dog'
    is_favorite: boolean
  }
}

DB1 and DB2 would be the name of my databases.

All of my databases share the same schema name, so I can just do something like the following:

import { Server } from "./schemas";

export function table<
  DB extends keyof Server,
  Table extends string & keyof Server[DB]
>(database: DB, table: Table) {
  return sql<Server[DB][Table]>`${sql.id(database, "dbo", table)}`;
}

With that, you can use it as such for a join:

const result = await db1.selectFrom("person")
  .innerJoin(table("DB2", "pet").as("pet"), "person.id", "pet.owner_id")
  .selectAll()
  .execute();

You can also use the json helpers as such:

const result = await db1.selectFrom("person")
  .selectAll("person")
  .select((eb) =>
    jsonArrayFrom(
      eb
        .selectFrom(table("DB2", "pet").as("pet"))
        .select(['pet.id', 'pet.name'])
        .whereRef("pet.owner_id", "=", "person.id")
    ).as("pets")
  )
  .execute();

Both of these keep the type safety without requiring explicit generics and allowing you to join across databases.

Apologies if any of this syntax is slightly off, I more or less took the example from kysely's relations recipe, modified it with the tables helper function and to fit the schemas in my databases. Then I subbed the example table's names and schemas back in, but I think this covers the gist of it.

Edit: here's a kysely playground link which might be a bit more digestible.