Graph database
lastmod 2023-08-01created 2017-01-185 edits
The Graph Model is a concept made up of nodes and relationships. Nodes and relationships can have any number of properties (key-value-pairs). A relationship basically has properties for direction, type, start node, and end node, plus additional properties, most of which are quantitative in nature. Examples are weight, costs, distances, ratings, time intervals, strengths, etc. A graph database has one constant core rule: "No broken links". That is, a relationship must always have a start node and an end node, which means a node cannot be deleted without deleting the relationship objects connected to it. It can also be assumed that an existing relationship cannot connect to a node that does not exist.
Looking at it again, you can think of a node as similar to a table, and properties as similar to table fields. Meta-like data such as constraints (primary key, foreign key, not null … ) and indexes that exist on a table are handled as node properties.