Lab3-DB_Neo4j

Lab3-DB_Neo4j

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  CS331 - DatabaseManagement Systems Dr. Lilia Sfaxi 17 novembre 2019 Neo4J 1. Graph-based Databases : Neo4J 1.1. Graphs Formally, a graph is a collection of nodes and arcs that connect them. The graphs represent the entities in the form of nodes, and the ways in which these entities are connected in the form of arcs. This structure inspired the graph- oriented databases, because they make it possible to model all types of scenarios. For example, the relationships between Twitter users can be represented in a simpli fi ed way by the following graph: A graph can represent any type of data. - A node is the equivalent of a record - A relation makes it possible to connect nodes, and can be typed - Nodes and relationships can have properties, representing named attributes - A label is a name allowing to organize the nodes in groups NEO4J DR. LILIA SFAXI 1 MedTech
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  The database wewill use in this lab is Neo4j . This database uses the Cypher 1 language to represent queries. 1.2.Example The example we will show in this manuscript is taken from the tutorial provided by Neo4j in their site on this link: http://neo4j.com/graphacademy/online- course/ The data we process represents: - Movies with a label : Movie and the properties title, released and tagline - People with a label : Person and the properties name and born - An ACTED_IN relation from an actor to a movie, with a roles property containing the list of character names - A DIRECTED relationship from a director to a fi lm. Activity 1 Launch Neo4J on your browser. The default login/password is neo4j/neo4j (they will ask you to change after fi rst authentication). Create the Movies database given as an example by the tool by following these steps: - Once authenticated and the default password replaced, choose: "Jump Into Code" to start developing. - Click on "Create a Graph" in the "Movie Graph" section as follows: Neo4J: http://neo4j.com/ 1 NEO4J DR. LILIA SFAXI 2
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  - In thewindow that appears, click on the graph creation code to load it into the editor. Then run it. 1.3.The Cipher Language Nodes (a) Actors (m) Films ( ) Anonymous Node Relations -[r]-> A relation called r (a) –[r]-> (m) Actors having a relation r with movies -[:ACTED_IN]-> The relation is of type ACTED_IN (a)-[:ACTED_IN]->(m) Actors who play in a movie (d)-[:DIRECTED]->(m) The directors of a fi lm Properties of Nodes (m {title : "The Matrix"}) Movie with a property title (a {name: "Keanu Reeves", born : 1964}) Actor with properties name and born NEO4J DR. LILIA SFAXI 3
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  Properties of Relations (a)-[ :ACTED_IN{roles :[« Neo »]}]->(m) Relation ACTED_IN with the propperty roles, which is an array of names Labels Allow to recognize different types of nodes. (a:Person)-[:ACTED_IN]->(m:Movie) A person who has played in a movie 1.4. Cipher queries 1.4.1. Simple read requests Here are some examples of Cipher queries: The fi rst statement returns the value of the property property for all nodes. The second one, returns the values of propertyA and propertyB of each pair of nodes node2 and node1 which are connected by a relation (whatever its nature). To return only nodes connected by a relation of type REL_TYPE: NEO4J DR. LILIA SFAXI 4
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  If the relationin question contains properties that one wishes to read, give it a name (here rel): To indicate a particular type of nodes, use the labels: It is possible to assign an identi fi er to a relation, then return the type of the relation, or its properties: To support by an example, consider the following graph: The query to fi nd all the characters in The Matrix movie is: NEO4J DR. LILIA SFAXI 5
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  Another way isalso possible to fi lter the data (instead of the traditional WHERE), by replacing the previous query by: Activity 2. Run the following queries in your editor: - Give all movies where Tom Hanks played - Give the list of all Matrix characters - Give each fi lm its release date 1.4.2. Paths A path is a set of connected nodes and relationships, which can be a pattern. For example : (a) -> (b) -> (c) (a) -> (b) <- (c) Example: To show all actors and directors of all movies: It is also possible to divide the query into several paths, as follows: Or: NEO4J DR. LILIA SFAXI 6
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  The results ofprevious queries are tables. It is possible to return the entire path, with all the properties of all nodes and relationships involved: If this is too much information, you can just select the nodes of the path: ... or only relationships: Activity 3. Execute the following queries in your editor: - Which directors have played in their own movies? - Give the movies where Keanu Reeves played the role of Neo. - Which actors have already played in the same movie with Tom Hanks, and in which fi lm? - Which actors played in the same movie with Tom Hanks, and with Keanu Reeves? - Who are the characters in the movie "The Matrix"? 1.4.3. Edit a graph with Cipher To add a node to the graph: To add (or modify) properties to an existing node: NEO4J DR. LILIA SFAXI 7
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  To add arelationship between two existing nodes: Activity 4. Run the following queries in your editor: - Create a movie called Mystic River - Add Kevin Bacon as an actor in the movie "Mystic River" with the role "Sean" - Change the role to become "Sean Devine" NEO4J DR. LILIA SFAXI 8