typeorm/docs/tables-and-columns.md

Tables and columns

Creating a basic table

Every object that you want to be saved in the database must have @Table decorator and each property you want to be saved from your object must have @Column decorator. Let's start with an example:

@Table("photo")
class Photo {
    
    @PrimaryColumn()
    id: number;
    
    @Column()
    name: string;
    
    @Column()
    filename: string;
    
    @Column()
    description: string;
    
}

• @Table decorator registers your class in ORM, and allows you to make different operations with instances of this class directly in the db. After you mark your class with this decorator and run schema update process, ORM will create a table in the db for you, with all proper columns, keys and so on. After you define your class as a @Table you can do various operations like inserting, updating, removing, fining objects of this class in the database. In this example we also specified a name for this table (@Table("photo")). ORM will create a table in the database with such name - "photos".

• @Column decorator marks properties of your class to be persisted into the database. For each property of your class decorated by @Table decorator ORM will create a column in the table, and this property's value will be saved to database when you'll save a class instance.

• @PrimaryColumn decorator marks a property of your class that must be a primary-key in your table. It works the same way as @Column decorator, but the main difference is that it also creates a PRIMARY KEY for this column. This decorator is always used when you want to create an id-based column, including auto-increment id.

Primary and regular columns

By default column type used in the database is automatically guessed from property type. But type that is set for property is not desirable for the type used in the database. For example type number You can specify a type of column that will be used @Column`

@Table("photo")
class Photo {
    
    @Column("string")
    name: string;
    
    @Column()
    filename: string;
    
    @Column()
    description: string;
    
}