constraint
A rule the database enforces on every node or relationship with a given label or type, rejecting any write that breaks it.
Also written: constraints
Example
Every (:Person) must hold a name.
cypher
CREATE CONSTRAINT Person_name_exists IF NOT EXISTS
FOR (p:Person) REQUIRE p.name IS NOT NULLA write creating a (:Person) without a name is rejected, and so is one removing the name from a person already in the graph. Either way the transaction fails and nothing is stored.
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