## Neo4j

> [Neo4j](https://neo4j.com/docs/getting-started/) is a graph database management system developed by `Neo4j, Inc`.

> The data elements `Neo4j` stores are nodes, edges connecting them, and attributes of nodes and edges. Described by its developers as an ACID-compliant transactional database with native graph storage and processing, `Neo4j` is available in a non-open-source “community edition” licensed with a modification of the GNU General Public License, with online backup and high availability extensions licensed under a closed-source commercial license. Neo also licenses `Neo4j` with these extensions under closed-source commercial terms.

> This notebook shows how to use LLMs to provide a natural language interface to a graph database you can query with the `Cypher` query language.

> [Cypher](https://en.wikipedia.org/wiki/Cypher_(query_language)) is a declarative graph query language that allows for expressive and efficient data querying in a property graph.

## Settin up[​](#settin-up "Direct link to Settin up")

You will need to have a running `Neo4j` instance. One option is to create a [free Neo4j database instance in their Aura cloud service](https://neo4j.com/cloud/platform/aura-graph-database/). You can also run the database locally using the [Neo4j Desktop application](https://neo4j.com/download/), or running a docker container. You can run a local docker container by running the executing the following script:

```
docker run \    --name neo4j \    -p 7474:7474 -p 7687:7687 \    -d \    -e NEO4J_AUTH=neo4j/pleaseletmein \    -e NEO4J_PLUGINS=\[\"apoc\"\]  \    neo4j:latest
```

If you are using the docker container, you need to wait a couple of second for the database to start.

```
from langchain.chains import GraphCypherQAChainfrom langchain_community.graphs import Neo4jGraphfrom langchain_openai import ChatOpenAI
```

```
graph = Neo4jGraph(    url="bolt://localhost:7687", username="neo4j", password="pleaseletmein")
```

## Seeding the database[​](#seeding-the-database "Direct link to Seeding the database")

Assuming your database is empty, you can populate it using Cypher query language. The following Cypher statement is idempotent, which means the database information will be the same if you run it one or multiple times.

```
graph.query(    """MERGE (m:Movie {name:"Top Gun"})WITH mUNWIND ["Tom Cruise", "Val Kilmer", "Anthony Edwards", "Meg Ryan"] AS actorMERGE (a:Actor {name:actor})MERGE (a)-[:ACTED_IN]->(m)""")
```

## Refresh graph schema information[​](#refresh-graph-schema-information "Direct link to Refresh graph schema information")

If the schema of database changes, you can refresh the schema information needed to generate Cypher statements.

```
Node properties are the following:Movie {name: STRING},Actor {name: STRING}Relationship properties are the following:The relationships are the following:(:Actor)-[:ACTED_IN]->(:Movie)
```

## Querying the graph[​](#querying-the-graph "Direct link to Querying the graph")

We can now use the graph cypher QA chain to ask question of the graph

```
chain = GraphCypherQAChain.from_llm(    ChatOpenAI(temperature=0), graph=graph, verbose=True)
```

```
chain.run("Who played in Top Gun?")
```

```
> Entering new GraphCypherQAChain chain...Generated Cypher:MATCH (a:Actor)-[:ACTED_IN]->(m:Movie {name: 'Top Gun'})RETURN a.nameFull Context:[{'a.name': 'Tom Cruise'}, {'a.name': 'Val Kilmer'}, {'a.name': 'Anthony Edwards'}, {'a.name': 'Meg Ryan'}]> Finished chain.
```

```
'Tom Cruise, Val Kilmer, Anthony Edwards, and Meg Ryan played in Top Gun.'
```

## Limit the number of results[​](#limit-the-number-of-results "Direct link to Limit the number of results")

You can limit the number of results from the Cypher QA Chain using the `top_k` parameter. The default is 10.

```
chain = GraphCypherQAChain.from_llm(    ChatOpenAI(temperature=0), graph=graph, verbose=True, top_k=2)
```

```
chain.run("Who played in Top Gun?")
```

```
> Entering new GraphCypherQAChain chain...Generated Cypher:MATCH (a:Actor)-[:ACTED_IN]->(m:Movie {name: 'Top Gun'})RETURN a.nameFull Context:[{'a.name': 'Tom Cruise'}, {'a.name': 'Val Kilmer'}]> Finished chain.
```

```
'Tom Cruise and Val Kilmer played in Top Gun.'
```

You can return intermediate steps from the Cypher QA Chain using the `return_intermediate_steps` parameter

```
chain = GraphCypherQAChain.from_llm(    ChatOpenAI(temperature=0), graph=graph, verbose=True, return_intermediate_steps=True)
```

```
result = chain("Who played in Top Gun?")print(f"Intermediate steps: {result['intermediate_steps']}")print(f"Final answer: {result['result']}")
```

```
> Entering new GraphCypherQAChain chain...Generated Cypher:MATCH (a:Actor)-[:ACTED_IN]->(m:Movie {name: 'Top Gun'})RETURN a.nameFull Context:[{'a.name': 'Tom Cruise'}, {'a.name': 'Val Kilmer'}, {'a.name': 'Anthony Edwards'}, {'a.name': 'Meg Ryan'}]> Finished chain.Intermediate steps: [{'query': "MATCH (a:Actor)-[:ACTED_IN]->(m:Movie {name: 'Top Gun'})\nRETURN a.name"}, {'context': [{'a.name': 'Tom Cruise'}, {'a.name': 'Val Kilmer'}, {'a.name': 'Anthony Edwards'}, {'a.name': 'Meg Ryan'}]}]Final answer: Tom Cruise, Val Kilmer, Anthony Edwards, and Meg Ryan played in Top Gun.
```

## Return direct results[​](#return-direct-results "Direct link to Return direct results")

You can return direct results from the Cypher QA Chain using the `return_direct` parameter

```
chain = GraphCypherQAChain.from_llm(    ChatOpenAI(temperature=0), graph=graph, verbose=True, return_direct=True)
```

```
chain.run("Who played in Top Gun?")
```

```
> Entering new GraphCypherQAChain chain...Generated Cypher:MATCH (a:Actor)-[:ACTED_IN]->(m:Movie {name: 'Top Gun'})RETURN a.name> Finished chain.
```

```
[{'a.name': 'Tom Cruise'}, {'a.name': 'Val Kilmer'}, {'a.name': 'Anthony Edwards'}, {'a.name': 'Meg Ryan'}]
```

## Add examples in the Cypher generation prompt[​](#add-examples-in-the-cypher-generation-prompt "Direct link to Add examples in the Cypher generation prompt")

You can define the Cypher statement you want the LLM to generate for particular questions

```
from langchain_core.prompts.prompt import PromptTemplateCYPHER_GENERATION_TEMPLATE = """Task:Generate Cypher statement to query a graph database.Instructions:Use only the provided relationship types and properties in the schema.Do not use any other relationship types or properties that are not provided.Schema:{schema}Note: Do not include any explanations or apologies in your responses.Do not respond to any questions that might ask anything else than for you to construct a Cypher statement.Do not include any text except the generated Cypher statement.Examples: Here are a few examples of generated Cypher statements for particular questions:# How many people played in Top Gun?MATCH (m:Movie {{title:"Top Gun"}})<-[:ACTED_IN]-()RETURN count(*) AS numberOfActorsThe question is:{question}"""CYPHER_GENERATION_PROMPT = PromptTemplate(    input_variables=["schema", "question"], template=CYPHER_GENERATION_TEMPLATE)chain = GraphCypherQAChain.from_llm(    ChatOpenAI(temperature=0),    graph=graph,    verbose=True,    cypher_prompt=CYPHER_GENERATION_PROMPT,)
```

```
chain.run("How many people played in Top Gun?")
```

```
> Entering new GraphCypherQAChain chain...Generated Cypher:MATCH (m:Movie {name:"Top Gun"})<-[:ACTED_IN]-(:Actor)RETURN count(*) AS numberOfActorsFull Context:[{'numberOfActors': 4}]> Finished chain.
```

```
'Four people played in Top Gun.'
```

## Use separate LLMs for Cypher and answer generation[​](#use-separate-llms-for-cypher-and-answer-generation "Direct link to Use separate LLMs for Cypher and answer generation")

You can use the `cypher_llm` and `qa_llm` parameters to define different llms

```
chain = GraphCypherQAChain.from_llm(    graph=graph,    cypher_llm=ChatOpenAI(temperature=0, model="gpt-3.5-turbo"),    qa_llm=ChatOpenAI(temperature=0, model="gpt-3.5-turbo-16k"),    verbose=True,)
```

```
chain.run("Who played in Top Gun?")
```

```
> Entering new GraphCypherQAChain chain...Generated Cypher:MATCH (a:Actor)-[:ACTED_IN]->(m:Movie {name: 'Top Gun'})RETURN a.nameFull Context:[{'a.name': 'Tom Cruise'}, {'a.name': 'Val Kilmer'}, {'a.name': 'Anthony Edwards'}, {'a.name': 'Meg Ryan'}]> Finished chain.
```

```
'Tom Cruise, Val Kilmer, Anthony Edwards, and Meg Ryan played in Top Gun.'
```

## Ignore specified node and relationship types[​](#ignore-specified-node-and-relationship-types "Direct link to Ignore specified node and relationship types")

You can use `include_types` or `exclude_types` to ignore parts of the graph schema when generating Cypher statements.

```
chain = GraphCypherQAChain.from_llm(    graph=graph,    cypher_llm=ChatOpenAI(temperature=0, model="gpt-3.5-turbo"),    qa_llm=ChatOpenAI(temperature=0, model="gpt-3.5-turbo-16k"),    verbose=True,    exclude_types=["Movie"],)
```

```
# Inspect graph schemaprint(chain.graph_schema)
```

```
Node properties are the following:Actor {name: STRING}Relationship properties are the following:The relationships are the following:
```

## Validate generated Cypher statements[​](#validate-generated-cypher-statements "Direct link to Validate generated Cypher statements")

You can use the `validate_cypher` parameter to validate and correct relationship directions in generated Cypher statements

```
chain = GraphCypherQAChain.from_llm(    llm=ChatOpenAI(temperature=0, model="gpt-3.5-turbo"),    graph=graph,    verbose=True,    validate_cypher=True,)
```

```
chain.run("Who played in Top Gun?")
```

```
> Entering new GraphCypherQAChain chain...Generated Cypher:MATCH (a:Actor)-[:ACTED_IN]->(m:Movie {name: 'Top Gun'})RETURN a.nameFull Context:[{'a.name': 'Tom Cruise'}, {'a.name': 'Val Kilmer'}, {'a.name': 'Anthony Edwards'}, {'a.name': 'Meg Ryan'}]> Finished chain.
```

```
'Tom Cruise, Val Kilmer, Anthony Edwards, and Meg Ryan played in Top Gun.'
```