Why resolve many to many relationship in a data model

But many-to-many relationships are a bit different. Like Join the DZone community and get the full member experience. Join For Free. There are three ways in which a table can be related to another table: One-to-one : A record in one table is related to one record in another table.

One-to-many : A record in one table is related to many records in another table. Many-to-many : Multiple records in one table are related to multiple records in another table. The rules are: A student can be enrolled in multiple classes at a time for example, they may have three or four classes per semester.

Browse our articles to find the answers you need. All Topics. Data Modeling. Data Relationships: Many-to-Many Relationship Resolutions For general information on types of data relationships, potential complications and how to resolve them, see the following articles:. There are several methods to resolve and bypass a many-to-many relationship; the solution depends on the business model and the logic of the business questions at hand. The following solutions differ by business logic and the schema at hand, each solution can be applied to each schema respectively.

Resolutions for 2 tables, one relationship. The direct solution for Many-to-Many would be to break this relationship into two separate one-to-many relationships, as seen the image below. The logic behind testing this issue can be visualized in the decision tree below. Follow the steps below to resolve the Many-to-Many this way:. If you create a Many-to-Many relationship between entities on the logical side and automatically insert an associative table between the two tables involved in a many-to-many relationship, you can change the relationship into a series of one-to-many relationships and use the new relationships to clarify how the data model works.

Account Settings Logout. All Files. Create a relationship between the two Student ID fields in the tables. Then create a relationship between the two Class ID fields in the tables. Using this design, if a student registers for three classes, that student will have one record in the Students table and three records in the Enrollments table—one record for each class the student enrolled in.

For example, to display a list of all the classes a student enrolled in, create a portal on a layout based on the Students table. Design the portal to show related records from the Classes table. Then add the appropriate fields from Classes to the portal.

As you browse through records in the Students layout, the portal displays all the classes a particular student is enrolled in. Planning a relational database.