Neo4J Interview Questions and Answers: If you’re preparing for a Neo4J Technical Interview, it’s essential to equip yourself with the Latest Neo4J Interview Questions and Answers. In this highly competitive world, staying ahead of the game requires you to have a solid understanding of the concepts and technologies in demand. Neo4J, a graph database management system, has gained immense popularity in recent years due to its efficiency and flexibility.
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Neo4J Technical Interview Questions
As a result, Neo4J Interview Questions for Freshers and experienced professionals alike have become more common. In this article, we have compiled the Top 100 Neo4J Interview Questions and Answers to help you prepare and ace your next Neo4J Interview.
Top 100 Neo4J Interview Questions and Answers 2023
1. What is Neo4j?
Answer: Neo4j is a graph database management system. It is designed to store and manage large volumes of connected data.
2. What are the important features of Neo4J?
Answer: Following are a few important features:
- Data Representation using a graph model
- Reliable ACID transactions.
- Quick and Durable.
- High-Speed query execution for traversals.
- Easily accessible by REST or Java APIs.
3. List out some of the Neo4J Commands
Answer: There are many commands in Neo4J, of which the following are few basic commands:
- CREATE – To create a node or relationship.
- CREATE UNIQUE – To mention unique constraints in order to avoid redundant values.
- MATCH – To read or retrieve all the nodes in the database.
- MERGE – Combination of CREATE and MATCH.
- SET – To add or update properties to new or existing nodes/relationships.
4. What is a graph database?
Answer: A graph database is a type of database that uses graph structures to store and represent data.
5. What is a graph?
Answer: A graph is a data structure that consists of nodes and edges, where nodes represent entities and edges represent relationships between those entities.
6. What are nodes and edges in a graph database?
Answer: Nodes are entities in a graph database, and edges represent relationships between those entities.
7. What is the difference between Neo4j Vs MongoDB?
Answer:
| Neo4j | MongoDB |
| A primary database model is Graph DBMS. | A primary database model is Document Store. |
| Implemented in Java and Scala. | Implemented in C++ Language. |
| Neo4j has an optional schema. | MongoDB is schema-free. |
| It uses Cypher query language, Java API, Neo4j-OGM, Spring Data Neo4j, TinkerPop 3 | Proprietary protocol using JSON |
| Uses triggers | No triggers are used |
8. What is Cypher?
Answer: Cypher is a declarative graph query language that is used to query Neo4j.
9. What is a relationship in Neo4j?
Answer: A relationship in Neo4j is a directed link between two nodes in a graph database.
10. What is a property in Neo4j?
Answer: A property in Neo4j is a key-value pair that is associated with a node or a relationship.
11. What is a transaction in Neo4j?
Answer: A transaction in Neo4j is a way of grouping database operations together into a single, atomic unit.
12. Explain the differences b/w RDBMS and Graph Database?
Answer:
| RDBMS | Graph Database |
|---|---|
| Tables | Graphs |
| Rows | Nodes |
| Columns and Data | Properties and its Values |
| Constraints | Relationships |
| Joins | Traversal |
13. How does Neo4j differ from a traditional relational database?
Answer: Neo4j differs from a traditional relational database in that it is optimized for handling highly connected data, whereas relational databases are optimized for handling structured data.
14. What are the benefits of using Neo4j?
Answer: The benefits of using Neo4j include better performance for highly connected data, more flexible data modeling, and easier queryability.
15. What is the role of building blocks in Neo4J?
Answer: Roles of building blocks:
- Nodes: They are entities equivalent to rows in table.
- Relationship: It connects entities and structure domain.
- Properties: It contains meta-data and attributes.
- Labels: It groups nodes by role.
16. What are the limitations of Neo4j?
Answer: The limitations of Neo4j include less support for complex joins and aggregations, and higher complexity for data modeling and query optimization.
17. What is a traversal in Neo4j?
Answer: A traversal in Neo4j is a way of traversing the graph to find specific nodes and relationships.
18. What is a path in Neo4j?
Answer: A path in Neo4j is a sequence of nodes and relationships that connect two or more nodes in the graph.
19. What are the differences between Neo4J Graph Database and MySQL?
Answer:
| Neo4J | MySQL |
|---|---|
| Neo4J contains vertices and edges. Each vertex or node represent a key value or attribute. | In MySQL, attributes are appended in plain table format. |
| It provides the capability of deep search into the database without affecting the performance along with efficient timing. | It takes longer time for database search and also inconvenient compared to Neo4J. |
| In Neo4j, two or more objects can be related by making relationship between them. | It lacks relationship and very difficult to use them for connected graphs and data. |
| In Neo4J, it is possible to store dynamic content like images, videos, audio etc. | In relational databases, such as MySQL, it is difficult to store videos, audios and images. |
20. What is a subgraph in Neo4j?
Answer: A subgraph in Neo4j is a portion of the graph that contains a subset of nodes and relationships.
21. What is a graph algorithm in Neo4j?
Answer: A graph algorithm in Neo4j is a set of computational procedures that are designed to solve problems on graphs.
22. What is graph visualization in Neo4j?
Answer: Graph visualization in Neo4j is a way of displaying the graph in a visual format, which can help users to better understand the data.
23. What are the different types of object caches in Neo4j?
Answer: Neo4j utilizes two types of object caches:
- Reference Caches, which utilize the entirety of the allocated JVM heap memory to store nodes and relationships, and
- High-Performance Caches, which have a designated maximum heap space and remove objects when it surpasses that limit.
24. What is a community detection algorithm in Neo4j?
Answer: A community detection algorithm in Neo4j is a type of graph algorithm that is used to identify communities or groups of nodes in the graph that are highly interconnected.
25. What is graph embedding in Neo4j?
Answer: Graph embedding in Neo4j is a way of representing the graph as a vector space, which can be used for machine learning applications.
26. What is a graph database model in Neo4j?
Answer: A graph database model in Neo4j is a way of organizing and structuring the data in the graph database. It defines the nodes, relationships, properties, and labels that are used to represent the data.
27. What is a property graph model in Neo4j?
Answer: A property graph model in Neo4j is a type of graph database model that consists of nodes, relationships, and properties.
28. What is a node-centric index in Neo4j?
Answer: A node-centric index in Neo4j is an index that is used to optimize queries that start with a specific node.
29. What is a relationship-centric index in Neo4j?
Answer: A relationship-centric index in Neo4j is an index that is used to optimize queries that start with a specific relationship.
30. What is a spatial index in Neo4j?
Answer: A spatial index in Neo4j is an index that is used to optimize queries that involve spatial data.
31. What is the difference between a full-text index and a regular index in Neo4j?
Answer: A full-text index in Neo4j is used to optimize queries that involve searching for text within properties, while a regular index is used to optimize queries that involve searching for a specific value in a property.
32. What is the difference between a unique constraint and a node key constraint in Neo4j?
Answer: A unique constraint in Neo4j is used to enforce that a property value must be unique across all nodes with the same label, while a node key constraint is used to enforce that a combination of property values must be unique for a specific label.
33. What is the difference between a directed and an undirected relationship in Neo4j?
Answer: A directed relationship in Neo4j is a relationship that has a direction, while an undirected relationship is a relationship that does not have a direction.
34. What is the difference between a node and a relationship property in Neo4j?
Answer: A node property in Neo4j is a property that is associated with a node, while a relationship property is a property that is associated with a relationship.
35. How can you import data into Neo4j?
Answer: Data can be imported into Neo4j using the Cypher query language, or by using the Neo4j import tool.
36. How can you export data from Neo4j?
Answer: Data can be exported from Neo4j using the Cypher query language, or by using the Neo4j export tool.
37. What is a stored procedure in Neo4j?
Answer: A stored procedure in Neo4j is a custom function that is written in Java and can be called from Cypher queries.
38. How can you optimize a Cypher query in Neo4j?
Answer: Cypher queries can be optimized in Neo4j by using indexes, constraints, and by rewriting the query to use more efficient patterns.
39. What is the difference between a scalar function and an aggregation function in Cypher?
Answer: A scalar function in Cypher returns a single value for each row, while an aggregation function returns a single value for a group of rows.
40. What is a subquery in Cypher?
Answer: A subquery in Cypher is a query that is nested inside another query.
41. What is a pattern comprehension in Cypher?
Answer: A pattern comprehension in Cypher is a way of returning a subgraph that matches a specific pattern.
42. What is a transaction function in Neo4j?
Answer: A transaction function in Neo4j is a custom function that is executed as part of a transaction.
43. What are some disadvantages of using a graph database like Neo4j over a relational database?
Answer: Disadvantages of using a graph database like Neo4j over a relational database include:
- Limited support for transactional consistency across multiple nodes
- Higher complexity and learning curve for data modeling and querying
- Less mature ecosystem of tools and libraries compared to relational databases
44. How does Neo4j handle transactions?
Answer: Neo4j uses ACID transactions to ensure data consistency and integrity. Transactions can be either read-only or read-write.
45. What is ACID?
Answer: ACID is an acronym that stands for Atomicity, Consistency, Isolation, and Durability. It is a set of properties that guarantee the reliability of database transactions.
46. What is the CAP theorem?
Answer: The CAP theorem states that it is impossible for a distributed system to simultaneously provide all three of the following properties: consistency, availability, and partition tolerance.
47. What is the difference between a Cypher query and a SQL query?
Answer: A Cypher query is used to query graph databases like Neo4j and represents data as a network of nodes and relationships, while a SQL query is used to query relational databases and represents data as tables.
48. How can you optimize the performance of a Cypher query?
Answer: You can optimize the performance of a Cypher query by using indexes, reducing the number of nodes and relationships accessed, and minimizing the use of expensive functions.
49. What is a label in Neo4j?
Answer: A label in Neo4j is a way to categorize nodes and relationships and create a type hierarchy.
50. How can you create a node with a specific label and properties in Neo4j?
Answer: You can create a node with a specific label and properties in Neo4j using the CREATE clause, for example:
| CREATE (n:Label {property1: value1, property2: value2}) |
51. How can you create a relationship between two nodes in Neo4j?
Answer: You can create a relationship between two nodes in Neo4j using the CREATE clause, for example:
| MATCH (node1:Label1), (node2:Label2) CREATE (node1)-[:RELATIONSHIP_TYPE]->(node2) |
52. How can you monitor the performance of Neo4j?
Answer: The performance of Neo4j can be monitored using the Neo4j Browser or by using third-party monitoring tools.
53. What is the Neo4j Browser?
Answer: The Neo4j Browser is a web-based interface that allows users to interact with Neo4j databases and execute Cypher queries.
54. How can you configure security in Neo4j?
Answer: Security in Neo4j can be configured by enabling authentication and authorization, configuring SSL/TLS encryption, and setting up firewall rules.
55. What is the difference between authentication and authorization in Neo4j?
Answer: Authentication in Neo4j is the process of verifying the identity of a user, while authorization is the process of determining whether a user has permission to perform a specific action.
56.
How can you update a property of a node in Neo4j?
Answer: You can update a property of a node in Neo4j using the SET clause, for example:
| MATCH (n:Label {property: value}) SET n.property = new_value |
57. How can you delete a node in Neo4j?
Answer: You can delete a node in Neo4j using the DELETE clause, for example:
| MATCH (n:Label {property: value}) DELETE n |
58. How can you delete a relationship in Neo4j?
Answer: You can delete a relationship in Neo4j using the DELETE clause, for example:
| MATCH (node1)-[r:RELATIONSHIP_TYPE]->(node2) DELETE r |
59. What are some key features of the Cypher query language?
Answer: Some key features of the Cypher query language include:
- Pattern matching: Cypher allows you to specify patterns of nodes and relationships in a graph.
- Expressive syntax: Cypher provides a concise and expressive syntax for querying graph databases.
- Aggregation and grouping: Cypher allows you to perform aggregations and group data in a graph.
- Path traversal: Cypher allows you to traverse paths in a graph and perform operations on the nodes and relationships along the path.
- Built-in functions: Cypher provides a set of built-in functions for performing operations on properties and values in a graph.
60. What is the difference between a node and a relationship in Neo4j?
Answer: A node in Neo4j represents an entity in a graph, while a relationship represents a connection between two nodes.
61. What is the difference between a property and an attribute in Neo4j?
Answer: In Neo4j, the terms property and attribute are often used interchangeably to refer to key-value pairs associated with nodes or relationships.
62. How can you use Cypher to find the shortest path between two nodes in Neo4j?
Answer: You can use the shortestPath() function in Cypher to find the shortest path between two nodes in Neo4j, for example:
| MATCH (start:Node {name: ‘A’}), (end:Node {name: ‘D’}) MATCH p = shortestPath((start)-[*]-(end)) RETURN p |
63. How can you start a transaction in Neo4j?
Answer: You can start a transaction in Neo4j by using the BEGIN clause, for example:
| BEGIN // database operations COMMIT |
64. What is the difference between a hot backup and a cold backup in Neo4j?
Answer: A hot backup in Neo4j is a backup that is taken while the database is running, while a cold backup is a backup that is taken while the database is offline.
65. What is the Neo4j sandbox?
Answer: The Neo4j sandbox is a cloud-based environment where users can experiment with Neo4j without having to install it on their own computer.
66. What is the difference between a graph database and a relational database?
Answer: A graph database represents data as a network of nodes and relationships, while a relational database represents data as a set of tables with defined relationships between them.
67. How can you commit a transaction in Neo4j?
Answer: You can commit a transaction in Neo4j by using the COMMIT clause, for example:
| BEGIN // database operations COMMIT |
68. How can you roll back a transaction in Neo4j?
Answer: You can roll back a transaction in Neo4j by using the ROLLBACK clause, for example:
| BEGIN // database operations ROLLBACK |
69. What is the difference between a read-only transaction and a read-write transaction in Neo4j?
Answer: A read-only transaction in Neo4j can only read data from the database and cannot modify data, while a read-write transaction can read and modify data.
70. How can you create a stored procedure in Neo4j?
Answer: You can create a stored procedure in Neo4j using the CREATE PROCEDURE clause, for example:
| CREATE PROCEDURE myProcedure(param1, param2) BEGIN // database operations END |
71. What is the Cypher query planner in Neo4j?
Answer: The Cypher query planner in Neo4j is a component that determines the most efficient way to execute a Cypher query.
72. What is the difference between a single query and a batched query in Neo4j?
Answer: A single query in Neo4j is a query that is executed in a single transaction, while a batched query is a collection of queries that are executed in a single transaction.
73. What is a constraint in Neo4j?
Answer: A constraint in Neo4j is a rule that enforces a condition on the data in a graph, such as ensuring that a property has a unique value.
74. How can you create a constraint in Neo4j?
Answer: You can create a constraint in Neo4j using the CREATE CONSTRAINT clause, for example:
| CREATE CONSTRAINT ON (n:Node) ASSERT n.name IS UNIQUE |
75. How can you add a label to a node in Neo4j?
Answer: You can add a label to a node in Neo4j using the SET clause, for example:
| MATCH (n:Node {name: ‘A’}) SET n:Label |
76. How can you remove a label from a node in Neo4j?
Answer: You can remove a label from a node in Neo4j using the REMOVE clause, for example:
| MATCH (n:Node:Label {name: ‘A’}) REMOVE n:Label |
77. What is the difference between a community edition and an enterprise edition of Neo4j?
Answer: The community edition of Neo4j is a free and open-source version of the database that is suitable for small-scale projects, while the enterprise edition is a commercial version that provides additional features and scalability for larger projects.
78. How can you monitor the performance of a Neo4j database?
Answer: You can monitor the performance of a Neo4j database using tools such as Neo4j Desktop, the Neo4j Browser, and third-party monitoring tools that integrate with Neo4j. You can also use techniques such as query profiling and logging to identify and diagnose performance issues.
79. What is the syntax for creating a new node with a label in Neo4j?
Answer: The syntax for creating a new node with a label in Neo4j is:
| CREATE (n:Label {property1: value1, property2: value2}) |
80. How can you backup and restore a Neo4j database?
Answer: You can backup and restore a Neo4j database using the tools provided by Neo4j, such as the neo4j-admin backup and neo4j-admin restore commands.
81. What is the syntax for creating a relationship between two nodes in Neo4j?
Answer: The syntax for creating a relationship between two nodes in Neo4j is:
| MATCH (n1:Label1 {property: value1}), (n2:Label2 {property: value2}) CREATE (n1)-[:RELATIONSHIP_TYPE]->(n2) |
82. What is APOC in Neo4j?
Answer: APOC is a library of procedures and functions for Neo4j that provides additional functionality beyond what is available in Cypher.
83. What is the Cypher query language?
Answer: The Cypher query language is a declarative language for querying graph databases like Neo4j.
84. What is the syntax for deleting a node in Neo4j?
Answer: The syntax for deleting a node in Neo4j is:
| MATCH (n:Label {property: value}) DELETE n |
85. What is the difference between a single-node and a clustered deployment of Neo4j?
Answer: A single-node deployment of Neo4j is a deployment where the database runs on a single server, while a clustered deployment is a deployment where the database runs on multiple servers and is distributed across them.
86. How can you backup and restore a Neo4j database?
Answer: A Neo4j database can be backed up and restored using the Neo4j backup and restore tools.
87. What are some advantages of using a graph database like Neo4j over a relational database?
Answer: Advantages of using a graph database like Neo4j over a relational database include:
- Ability to model complex and connected data more easily
- Higher performance for complex queries involving relationships
- Ability to handle unstructured and semi-structured data more easily
- Better scalability for large and complex datasets
88. What is the syntax for deleting a relationship in Neo4j?
Answer: The syntax for deleting a relationship in Neo4j is:
| MATCH (n1:Label1 {property: value1})-[r:RELATIONSHIP_TYPE]->(n2:Label2 {property: value2}) DELETE r |
89. What is the syntax for updating a property of a node in Neo4j?
Answer: The syntax for updating a property of a node in Neo4j is:
| MATCH (n:Label {property: value}) SET n.property = new_value |
90. What is the syntax for adding a new property to a node in Neo4j?
Answer: The syntax for adding a new property to a node in Neo4j is:
| MATCH (n:Label {property: value}) SET n.new_property = new_value |
91. How does Neo4j handle partition tolerance?
Answer: Neo4j uses a master-slave architecture to handle partition tolerance. The master node coordinates transactions and replicates data to slave nodes.
92. What is the difference between a primary key and a foreign key in Neo4j?
Answer: A primary key in Neo4j is a property or set of properties that uniquely identify a node, while a foreign key is a property that references a primary key in another node.
93. How does Neo4j handle concurrency control?
Answer: Neo4j uses optimistic concurrency control to ensure that transactions do not conflict with each other. Transactions are only applied if there are no conflicts with other transactions.
94. What is the syntax for removing a property from a node in Neo4j?
Answer: The syntax for removing a property from a node in Neo4j is:
| MATCH (n:Label {property: value}) REMOVE n.property |
95. What is the syntax for returning all nodes with a specific label in Neo4j?
Answer: The syntax for returning all nodes with a specific label in Neo4j is:
| MATCH (n:Label) RETURN n |
96. What is the syntax for returning nodes with a specific label and property value in Neo4j?
Answer: The syntax for returning nodes with a specific label and property value in Neo4j is:
| MATCH (n:Label {property: value}) RETURN n |
97. What is an index in Neo4j?
Answer: An index in Neo4j is a data structure that allows faster access to nodes or relationships based on specific properties.
98. What types of indexes are available in Neo4j?
Answer: The types of indexes available in Neo4j include:
- Node indexes
- Relationship indexes
- Full-text indexes
99. What is the difference between a unique constraint and a node property existence constraint in Neo4j?
Answer: A unique constraint ensures that a property or combination of properties is unique among all nodes, while a node property existence constraint ensures that a property exists on all nodes of a specific label.
100. What is the syntax for limiting the number of results returned in Neo4j?
Answer: The syntax for limiting the number of results returned in Neo4j is:
| MATCH (n:Label) RETURN n LIMIT 10 |
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