Databases : understand how to organize and to use data

Neo4j Exercise (credits : neo4j cookbook)

In this tutorial, you'll have to import the following script : dump

• Once the import is completed, then display all the nodes and edges
• How to get mutual friends of Annie and Lisa?
• How to get only the count of mutual friends of Annie and Lisa?
• How to get mutual friends of Annie with whoever on the graph?
• How to get the list of persons that share the most mutual friends in this graph?

Neo4j Exercise: friends exercises

• Display all the nodes and edges :

  MATCH (a)-[:'FRIEND']->(b) RETURN a,b

• How to get mutual friends of Annie and Lisa? :

  MATCH (someone)-[:FRIEND]->(mf)<-[:FRIEND]-(other)
  //identify a node which is at the same time a friend of "someone" and a friend of "other"
  WHERE  someone.name = "Annie" and other.name = "Lisa"
  //"other" is set to "Lisa" and "someone" is "Annie"
  RETURN mf.name

Neo4j Exercise: friends exercises

• Count all the mutual friends of Annie and Lisa :

  MATCH (someone)-[:FRIEND]->(mf)<-[:FRIEND]-(other)
  //identify a node which is at the same time a friend of "someone" and a friend of "other"
  WHERE  someone.name = "Annie" and other.name = "Lisa"
  //"other" is set to "Lisa" and "someone" is "Annie"
  RETURN count(mf)

• How to get mutual friends of Annie with whoever on the graph?

  MATCH (someone)-[:FRIEND]->(mf)<-[:FRIEND]-(other)
  //identify a node which is at the same time a friend of "someone" and a friend of "other"
  WHERE  someone.name = "Annie"
  //"other" can be whoever and "someone" is "Annie"
  RETURN mf.name

Neo4j Exercise: friends exercises

• How to get the list of persons that share the most mutual friends with Annie?

  OPTIONAL MATCH (someone)-[:FRIEND]->(mf)<-[:FRIEND]-(other)
              //get all the nodes with common friends, OPTIONAL will allow to fetch the results even incomplete,
              // due to that only part of the clause is verified.
              RETURN someone.name AS Friend1, other.name AS Friend2, count(mf) AS Count
              //return the name of the connected nodes, and their associated count
              ORDER BY count(mf) DESC LIMIT 2

Neo4j Practical Work : Space travelling

• The goal of this practical work is to see the power of neo4j in action thanks to a database inspired from star wars
• The problem solved by neo4j quite easily here is the Santa Claus problem , which resides in the fact that traversing a graph can have different costs providing a given source node and target node, depending on the path your are taking
• Load those cypher data

Neo4j Practical Work : Exploring space

• SW1. Display the graph
• SW2. What are the different nodes and label types?
• SW3. count the number of each node type

MATCH (l:Label) RETURN count(l) as Labels

Galaxy topology

• We have Planets, Sectors, Regions and Political systems, you can find a "group by count" equivalent hereafter:

  MATCH (n)
  RETURN DISTINCT count(labels(n)), labels(n);

• We can navigate from planets to planets thanks to the NEIGHBOR_OF (regular space travel) or ADJACENT_TO (hyperspace travel)

Neo4j Practical Work : Exploring space (2)

• SW4. List the isolated planets (what is an isolated planet?)
• SW5. What are the most populated sectors?
• SW6. List the 5 longest hyperspace routes