neo4j Cypher hierarchical tree build response to JSON

Question

Can you help me to build cypher query? i have following graph db structure:

(parent:Category)-[:subcategory]->(child:Category)


        

Answer 1

Cypher is not well suited for dumping out graph data in a tree structure when leaves are at arbitrary depths.

However, with neo4j 3.x, you can get close to what you want if you are able to install the APOC plugin on your server and use the apoc.convert.toTree procedure.

First, let's create some sample data:

CREATE
  (c1:Category {name: 'PC'}),
    (c1)-[:subcategory]->(c2:Category {name: 'Parts'}),
      (c2)-[:subcategory]->(c3:Category {name: 'CPU'}),
        (c3)-[:subcategory]->(c4:Category {name: 'CacheRAM'}),
    (c1)-[:subcategory]->(c5:Category {name: 'Accessories'}),
      (c5)-[:subcategory]->(c6:Category {name: 'Mouse'}),
      (c5)-[:subcategory]->(c7:Category {name: 'Keyboard'}),
  (c10:Category {name: 'Laptop'}),
    (c10)-[:subcategory]->(c20:Category {name: 'Parts'}),
      (c20)-[:subcategory]->(c30:Category {name: 'CPU'}),
    (c10)-[:subcategory]->(c40:Category {name: 'Accessories'}),
      (c40)-[:subcategory]->(c50:Category {name: 'Stylus'});

Then with this query:

MATCH p=(n:Category)-[:subcategory*]->(m)
WHERE NOT ()-[:subcategory]->(n)
WITH COLLECT(p) AS ps
CALL apoc.convert.toTree(ps) yield value
RETURN value;

... you will get N result rows, where N is the number of root Category nodes. Here is a snippet of sample results:

{
  ...
      "row": [
        {
          "_id": 150,
          "_type": "Category",
          "name": "PC",
          "subcategory": [
            {
              "_id": 154,
              "_type": "Category",
              "name": "Accessories",
              "subcategory": [
                {
                  "_id": 156,
                  "_type": "Category",
                  "name": "Keyboard"
                },
                {
                  "_id": 155,
                  "_type": "Category",
                  "name": "Mouse"
                }
              ]
            },
            {
              "_id": 151,
              "_type": "Category",
              "name": "Parts",
              "subcategory": [
                {
                  "_id": 152,
                  "_type": "Category",
                  "name": "CPU",
                  "subcategory": [
                    {
                      "_id": 153,
                      "_type": "Category",
                      "name": "CacheRAM"
                    }
                  ]
                }
              ]
            }
          ]
        }
      ],
  ...
      "row": [
        {
          "_id": 157,
          "_type": "Category",
          "name": "Laptop",
          "subcategory": [
            {
              "_id": 158,
              "_type": "Category",
              "name": "Parts",
              "subcategory": [
                {
                  "_id": 159,
                  "_type": "Category",
                  "name": "CPU"
                }
              ]
            },
            {
              "_id": 160,
              "_type": "Category",
              "name": "Accessories",
              "subcategory": [
                {
                  "_id": 161,
                  "_type": "Category",
                  "name": "Stylus"
                }
              ]
            }
          ]
        }
      ],
  ...
}