belongTo

BelongTo is a term used in data modeling and software development to describe an association in which a child entity is linked to a single parent entity. It expresses ownership or dependence: the child belongs to the parent.

In object-relational mapping frameworks, belongTo defines a many-to-one relationship from the child to the parent. The child table stores a foreign key referencing the parent’s primary key, enabling queries that retrieve the parent from the child and vice versa.

Ruby on Rails uses the belongs_to association to declare this relationship in models. For example, a Comment model might include belongs_to :post, which implies a post_id column on the comments table. In Rails, the association is validated by default for presence of the parent unless the optional: true flag is used (Rails 5 and later).

Laravel, a PHP framework, represents the relationship with a belongsTo method on the child model. For instance, public function post() { return $this->belongsTo(Post::class); } indicates that the child table contains a post_id foreign key pointing to the posts table. Customization is possible by specifying foreign keys and related keys.

From a database perspective, belongTo relies on foreign key constraints to enforce referential integrity and supports typical indexing for efficient joins. The behavior on deletion and updates is often configured at the database level or in the framework’s relationship options. The belongsTo relationship is complemented by inverse associations such as hasOne and hasMany, which model the corresponding parent-to-children direction.

In practice, belongTo is a foundational concept in many ORMs, used to model ownership, containment, or dependency where multiple child records refer to a single parent.