Many to relationship in example

Configure Many-to-Many Relationship in Code First

many to relationship in example

The relationship can be modeled in two ways using MongoDB. An example is a Blog where a blog might have many Comments but a Comment is only. One-to-many & many-to-many relationships are not the property of the data rather the relationship itself. And yes you do need bridging/third. Relationship types. One-to-one. One-to-many. Many-to-many. Many-to-many relationships and junction tables. Example 1: Students and classes. Example 2.

A student can register for many classes, and a class can include many students. The following example includes a Students table, which contains a record for each student, and a Classes table, which contains a record for each class. A join table, Enrollments, creates two one-to-many relationships—one between each of the two tables. The primary key Student ID uniquely identifies each student in the Students table.

many to relationship in example

The primary key Class ID uniquely identifies each class in the Classes table. To set up a join table for a many-to-many relationship: Using the example above, create a table named Enrollments.

  • Many-to-many relationships
  • Schema Basics
  • Configure Many-to-Many Relationships in Code-First

This will be the join table. Join tables typically hold fields that might not make sense to have in any other table. What might not be acceptable for a high write volume application might be tolerable for an application with low write load.

Many-to-many relationships

The third problem is exposed when one tries to perform pagination of the comments. There is no way to limit the comments returned from the Blog Post using normal finds so we will have to retrieve the whole blog document and filter the comments in our application.

Linking The second approach is to link comments to the Blog Post using a more traditional foreign key. Some example Comment documents with Foreign Keys An advantage this model has is that additional comments will not grow the original Blog Post document, making it less likely that the applications will run in the maximum document size of 16 MB. It's also much easier to return paginated comments as the application can slice and dice the comments more easily.

many to relationship in example

On the downside if we have comments on a blog post, we would need to retrieve all documents causing a lot of reads from the database.

Bucketing The third approach is a hybrid of the two above.

Additional Information

Basically, it tries to balance the rigidity of the embedding strategy with the flexibility of the linking strategy. For this example, we will split the comments into buckets with a maximum of 50 comments in each bucket. Some example Comment buckets The main benefit of using buckets in this case is that we can perform a single read to fetch 50 comments at a time, allowing for efficient pagination.

Typical cases where bucketing is appropriate are ones such as bucketing data by hours, days or number of entries on a page like comments pagination. M relationship is an example of a relationship between two entities where they both might have many relationships between each other.

An example might be a Book that was written by many Authors.

many to relationship in example

At the same time an Author might have written many Books. M relationships are modeled in the relational database by using a join table. A good example is the relationship between books and authors.

many to relationship in example

An author might have authored multiple books 1: A book might have multiple authors 1: This leads to an N: Now, we have four 4 categories. So, we create a product and assign the two categories to one product. First, create a ProductController using the following command. Now, I am using GET request for the saving the data because, we have not created the form, so we take every data manually.

Laravel Many To Many Relationship Example

Also, Now, what we are going to do is that we will create one Product that belongs To Many Categories. Now, God of War belongs to two categories. Video Games Playstation So, when we create a product, we also need to fill the pivot table with the two categories.

Since we just need an ID of categories, so right now, I have coded manually, but in real-time, you have those ids in the form request. Each row has a relationship with its product and category.