Finding All Child Entities using Query to Parent Entity in TypeORM

Question

Consider a base entity as below:

export abstract class Notification {
  @PrimaryGeneratedColumn()
  id: number;

  @Column({type: "date",nullable: false})
  seenAt: Date;

  @Column({ type: "integer", nullable: false })
  priority: number;
}

and two child entities as below:

@Entity()
export class NotificationType1 extends Notification {}

and

@Entity()
export class NotificationType2 extends Notification {}

Is there a way to find all rows in NotificationType1 and NotificationType2 using a query to the parent class like this?

SELECT * FROM NOTIFICATION;

This query return 0 rows, although there are records in NotificationType1 and NotificationType2 tables.

Answer 1

You should be able to Select from the superclass and retrieve all the records with something like this:

import {getConnection} from "typeorm"; 

const user = await getConnection().createQueryBuilder() 
.select("notification") 
.from(Notification, "notification");

You also need to change your abstract class to @TableInheritance to leverage Single Table Inheritance.

This Code:

export abstract class Notification {
  @PrimaryGeneratedColumn()
  id: number;

  @Column({type: "date",nullable: false})
  seenAt: Date;

  @Column({ type: "integer", nullable: false })
  priority: number;
}

Would become:

@Entity()
@TableInheritance({ column: { type: "varchar", name: "type" } })
export class Notification {
  @PrimaryGeneratedColumn()
  id: number;

  @Column({type: "date",nullable: false})
  seenAt: Date;

  @Column({ type: "integer", nullable: false })
  priority: number;
}

And the Child Entity:

@ChildEntity()
export class NotificationType1 extends Notification {}

The docs have on single table inheritance.