Database with TypeORM
Entities, repositories, relations, migrations, query builder, transactions, cascades
1What is an Entity in TypeORM?
What is an Entity in TypeORM?
回答
An Entity in TypeORM is a TypeScript class decorated with @Entity() that represents a database table. Each instance of the Entity corresponds to a row in the table. Class properties are automatically mapped to table columns using decorators like @Column().
2Which decorator to use to mark a property as a column in TypeORM?
Which decorator to use to mark a property as a column in TypeORM?
回答
The @Column() decorator transforms a class property into a database column. TypeORM automatically infers the SQL type from the TypeScript type, but it can be explicitly specified with @Column('varchar', { length: 255 }). This decorator is essential for all columns except the primary key.
3What is the difference between @PrimaryColumn() and @PrimaryGeneratedColumn()?
What is the difference between @PrimaryColumn() and @PrimaryGeneratedColumn()?
回答
@PrimaryGeneratedColumn() creates a primary key auto-incremented by the database, ideal for numeric identifiers. @PrimaryColumn() defines a primary key whose value must be provided manually, useful for UUID identifiers or composite keys. For most cases, using @PrimaryGeneratedColumn() is simpler and safer.
How to inject a TypeORM repository into a NestJS service?
Which decorator to use to define a nullable column in TypeORM?
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