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HomeJavascriptAPI with NestJS # 121. Many-to-one connections with PostgreSQL as well as...

API with NestJS # 121. Many-to-one connections with PostgreSQL as well as Kysely

Creating connections is just one of the essential elements of collaborating with SQL data sources. In this write-up, we proceed utilizing Kysely with NestJS as well as carry out many-to-one connections.

Have A Look At this database if you intend to see the complete code from this write-up.

Presenting the many-to-one connection

When applying the many-to-one connection, a row from the very first table is linked to numerous rows in the 2nd table. What’s crucial, a row from the 2nd table can link to simply one row from the very first table.

An instance is a post with a solitary writer, while the customer can be a writer of lots of write-ups. A method to apply it is to conserve the writer’s id in the.
table as a international secret An international secret is a worth that matches a column from a various table.

Whenever we develop an international type in our data source, PostgreSQL specifies the international vital restriction to make certain the uniformity of our information. Many thanks to that, it stops us from having an.
worth that describes a customer that does not exist. We can not:

  • develop a post as well as offer the.
    that indicates a customer that can not be discovered in the.
  • upgrade an existing write-up as well as transform the.
    to match a customer that does not exist,
  • erase a customer with an id utilized in the.

    • we would certainly need to erase the write-up initially or transform its writer
    • additionally, we can make use of the.
      choice to compel PostgreSQL to erase all write-ups the erased customer is a writer of

Specifying the many-to-one connection with Kysely

In among the previous components of this collection, we found out just how to create SQL movements when utilizing Kysely. This moment, we intend to include the.
column that is not nullable Sadly, we may currently have some write-ups in our data source, as well as including a brand-new non-nullable column without a default worth would certainly create a mistake.

MISTAKE: column “author_id” of relationship “write-ups” has void worths

To address the above trouble, we can offer a default worth for the.
column. To do that, we require to have a default customer. Allow’s include a seed documents to our.
directory site. Producing seed documents is a method to inhabit our data source with first information.

Including the seed documents

Initially, allow’s include the e-mail as well as password of the admin to the setting variables.


Currently we can include the seed documents to our movements.

20230817223154_insert_admin. ts


column, we can carry out the complying with strategy: include the.

  1. author_id
  2. column as nullable, author_id
  3. column for write-ups that do not have it, author_id
  4. column non-nullable. 1









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; import {



‘ @nestjs/ typical’





We need to carry out 2 signs up with to quiz the write-up, writer, as well as feasible address. articles.service.ts 1 2 3

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