unique constraint
A constraint that permits only one node or relationship with a given property value for its label or type.
Example
No two (:Movie) nodes may hold the same movieId.
cypher
CREATE CONSTRAINT Movie_movieId_unique IF NOT EXISTS
FOR (m:Movie) REQUIRE m.movieId IS UNIQUEA write creating a second (:Movie) with a movieId already in the graph is rejected, and its transaction fails. A (:Movie) carrying no movieId at all is stored, because the constraint compares the values that exist.
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