Constraints and Indexes in Neo4j

A constraint is implemented internally as an index and is used to constrain what is added to the graph. There are three types of constraints you can define:

• Uniqueness for a single nodeA vertex in a graph. In a property graph it can carry labels and properties. propertyA named value stored on a node or a relationship. value.
• Existence for a property of a node or relationshipA named, directed connection between two nodes. Every relationship has a type, a start node and an end node..
• Existence and uniqueness for a set of node property values (called a Node key).