35. Relational model diagrams

To understand the data model of a company or a product feature it usually helps to draw a diagram. The type of relationship between tables is reflected in the line that connects tables.

one-to-one

A simple line represents a one-to-one relationship. A dot highlights the table that has a foreign key. Here’s how we would represent the relationship between users and profile (user has one profile):

One to one

one-to-many

To highlight a one-to-many relationship we need to connect tables with a line that resembles a fork. Records from a table with a single line (...

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