https://github.com/zain-ul-din/neo4j-notes
Neo4j graph database notes for learning
https://github.com/zain-ul-din/neo4j-notes
Last synced: 3 months ago
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Neo4j graph database notes for learning
- Host: GitHub
- URL: https://github.com/zain-ul-din/neo4j-notes
- Owner: Zain-ul-din
- License: mit
- Created: 2024-09-02T11:00:55.000Z (about 1 year ago)
- Default Branch: main
- Last Pushed: 2024-09-05T07:10:48.000Z (about 1 year ago)
- Last Synced: 2025-06-27T17:56:46.068Z (3 months ago)
- Size: 37.1 KB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
## Neo4j Notes
Neo4j is a native graph database that lets us build nodes and relationships effortlessly.
### Terms
**Cypher:** is a query language in neo4j that lets us query data from a graph.
### Run Neo4j locally
To run neo4j locally install docker on your os and run the following command that will pull the docker image and run it,
```bash
docker run -dit --rm --name=my-neo4j -p 7474:7474 -p 7687:7687 --env=NEO4J_AUTH=none neo4j
```
flags explanation:
- `-p` 7474:7474 exposes the Neo4j browser interface on port 7474.
- `-p` 7687:7687 exposes the Bolt protocol for Cypher queries on port 7687.
- `--env=NEO4J_AUTH=` sets the default username and password (neo4j/test).
to run neo4j REPL run the following command that will let us interact with the database using `cypher` or commands
```bash
docker exec -it my-neo4j cypher-shell
```
**OR**
```bash
winpty docker exec -it my-neo4j cypher-shell
```
### Basic Cypher Queries
#### Insert a node:
Syntax for inserting a node
```cypher
CREATE (variable_name: LABEL { ...props });
```
example:
```cypher
CREATE (s1:Site {url: 'https://www.google.com', title: 'Google', description: 'The world\'s most popular search engine.'});
```
example of node insertion with timestamp,
```cypher
CREATE (f:Folder { name: 'Tech', createdAt: datetime() });
```
#### Visualize your data:
Neo4j provides a browser experience that allows us to see a visual representation of our data. to open it go to [http://localhost:7474/browser/](http://localhost:7474/browser/) and set the authentication type to none since we are just running locally.
to see all the data paste `MATCH (n) RETURN n` inside the code cell and run it
### Relationships
Syntax to create relationship:
```cypher
CREATE (NODE)-[:LABEL]->(NODE)
```
- `NODE:` Represents a node in the graph.
- `LABEL:` Represents the type of relationship between nodes.
In our case, A folder can contain many sites. To link sites to the folder run the following query,
```cypher
MATCH (f:Folder {name: 'Tech'}), (s:Site)
WHERE s.url IN ['https://www.github.com', 'https://www.stackoverflow.com']
CREATE (f)-[:CONTAINS]->(s)
RETURN f, s;
```
#### Nested relationship
To create a nested relationship where a folder is inside another folder, run the following query:
```cypher
MATCH (f:Folder)
WHERE f.name = 'Tech'
CREATE (newFolder:Folder { name: 'Web', createdAt: datetime() })
CREATE (f)-[:CONTAINS]->(newFolder)
RETURN f, newFolder;
```
To insert a new site in a nested folder run:
```cypher
MATCH (f:Folder) WHERE f.name = 'Web'
CREATE (s:Site {
url: 'https://developer.mozilla.org/en-US/',
title: 'MDN',
description: 'The MDN Web Docs site provides information about Open Web technologies including HTML, CSS, and APIs for both Web sites and progressive web apps'
})
CREATE (f)-[:CONTAINS]->(s)
RETURN f,s;
```
Query to add multiple sites at once:
```cypher
MATCH (f:Folder) WHERE f.name = 'Web'
UNWIND [
{ url: 'https://reactjs.org/', title: 'React', description: 'A JavaScript library for building user interfaces.' },
{ url: 'https://nodejs.org/', title: 'Node.js', description: 'A JavaScript runtime built on Chrome\'s V8 JavaScript engine.' },
{ url: 'https://docs.nestjs.com/', title: 'NestJS', description: 'A progressive Node.js framework for building efficient, reliable, and scalable server-side applications.' }
] AS site
CREATE (s:Site {
url: site.url,
title: site.title,
description: site.description
})
CREATE (f)-[:CONTAINS]->(s)
RETURN f, s;
```
> In Neo4j's Cypher query language, the `UNWIND` clause is used to transform a list of values into individual rows. Essentially, it "unwraps" a list so that each item in the list becomes a separate row in the result set. This is particularly useful when you want to perform operations on multiple items within a single query.
### Relationship Queries
Query to get all descendants of a node,
```cypher
MATCH (f:Folder)
WHERE f.name = 'Tech'
OPTIONAL MATCH (f)-[:CONTAINS*]->(descendants)
RETURN DISTINCT descendants;
```
We can also specify a depth how deep we want to query using this query:
In this case, we are specifying depth 1 and saying just querying direct children.
```cypher
MATCH (f:Folder)
WHERE f.name = 'Tech'
OPTIONAL MATCH (f)-[:CONTAINS*1]->(descendants)
RETURN DISTINCT descendants;
```
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