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Neo4j Interview Questions and Answers
Q. What is Neo4j?
An open source graph database of NOSQL that has an online backup and is implemented using Java is known as Neo4j. The user can also access it using software that is written in some other language and this achieved with the help of Cypher Query language that is implemented through a binary protocol or HTTP endpoint which is transactional. The data structures are saved in graphs rather than in tables in case of Neo4j.
Q. What is the query language that is used by Neo4j?
The query language that is used by Neo4j is the Cypher language. This Cypher language is considered to be a declarative language that is inspired by SQL. It is used for giving a description of patterns with the use of ASCII-art syntax in graphs.
Q. On which query language is Cypher based on? What three clauses and mention their uses?
You can say that Cypher language is based on SQL. Also, the property graph model is the basis of Cypher language.
In Cypher language there are several kinds of clauses. Among them, the most commonly used clauses are Match, Where and Return. Their functions are a little bit different from SQL
1. Match clause is utilized for giving a description of the structure of the pattern that is searched mainly on the basis of relationships.
2. The Where clause is used for adding more constraints to the patterns
3. The Return clause is used for defining those values which will be returned.
Q. Mention the type of values that should be present in the node of the graph database.
In Neo4j a node contains labels and properties and it is mainly used to represent entities but for this purpose, it is dependent on the relationships of the domain. The type of value that is present in these nodes is key-value pairs.
Q. What do you mean by traversal in Neo4j?
In order to find paths through graphs, traversal is used for navigation purpose. It is the process that will help you to query a graph and it will navigate through each node and begin from the starting node to related nodes in order to find answers.
Q. Mention the process of accessing the interface of Neo4j?
After you have downloaded the Neo4j and installed it, you can use the interface of Neo4j by directly accessing it through http://127.0.0.1:7474/Neo4j.
Q. Mention the usage of Create Unique.
In Neo4j, the Create unique clause is a combination of Create and match clauses. With the help of this, the user can create what is missing and also match. But now, this clause is not used and instead of it, Merge clause is used.
Q. Mention the language in which the Neo4j was developed.
The language that is used for developing Neo4j is Java.
Q. Mention the writing clauses of Cypher Query and also write about their uses.
1. With the use of Create clause, the user will be able to create nodes and relationships.
2. The Delete clause will allow the user to delete nodes, paths, and relationships. If you delete a node it is mandatory that the relationships that are associated with it should also be deleted.
3. With the help of Detach Delete clause, you will be able to delete a node or sets of nodes.
4. The process of updating labels of nodes and the properties on relationships and nodes are done by Set clause.
5. In order to remove labels from relationships and nodes make use of Remove clause.
Q. What are the clauses used for importing data?
1. There are two ways in which you can import data in Neo4j.
2. If you want to import data in CSV files, the user can make use of Load CSV clause.
3. Another method is to use periodic commit. This method is used when the user is importing large sets of data from CSV files. This clause is also helpful in minimizing out-of-memory related errors.
Q. Describe the scheme clauses.
The schema clauses are:-
1. The index of a node that has a particular label and property can be created or dropped by Create or Drop constraint respectively.
2. Then there is the Create or Drop index which is useful in dropping or Creating a constraint which is pertaining to a relationship type or node label and a property.
Q. Mention three perfunctory functions of Neo4j and also mention their uses.
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Exist - this function will show the result to be true if there is an occurrence of a match in the pattern of the graph or if there is a presence of a specified property in nodes, relationships or map.
All - it will return the result to be true if the predicated holds for each and every element of the list.
Any - it will return the result to be true if any one of the predicates holds for at least one element of the list.
Q. Mention three scalar functions and their uses.
1. Properties - it will return the map that holds all the properties of a relationship or node.
2. ToInteger - thus function is used to convert any string value or floating value to integer value.
3. Type - this function is used when the user wants to have a string representation of the relationship type.
Q. Mention three aggregating function and their uses.
PercentileCont - using the linear interpolation method over a group a value is generated and this function gives the percentile of the value.
1. Avg - it will return the average value of a group of numeric values.
2. Count - the number of rows or values will be returned by this function.
Q. What do you mean by object cache? Mention the types.
Object Cache is the method that is used to cache each and every node and relationships which all include their properties. These properties are optimized so that there can be a faster rate of traversal of the graph. In Neo4j there are two types of object cache-
1. High-performance cache
2. Reference cache
Q. Mention some of the features of the database of Neo4j.
1. It is fast and also durable.
2. It supports ACID transactions which makes it reliable.
3. It has the capability of supporting several billions of nodes, relationships, and maps.
4. It has a fast rate of traversal framework and it results in a faster rate of execution of the query.
Q. Mention the indexing capabilities for Neo4j.
The system of indexing that is valid in Neo4j is an ideal way of finding the start points in case of traversal of graphs.
Q. What is considered to be faster, Neo4j or MySql?
Neo4j is considered to be faster.
Q. What do you mean by list functions and mention three of them with their uses?
The list function will return the list of other values.
1. Extract - this function will return a list that will contain those values that are received from those expressions that have been already applied to every element present in the list.
2. Nodes - this function provides you with a list of each and every node present in the path.
3. Tail - this function will return each and every element in the list except the first one.
Q. Mention the architecture that will allow the usage of Neo4j on a server that is remote.
The Rest architecture will allow you to use Neo4j on a server that is remote in nature.
Q. In which form is information stored in Neo4j database?
Different files are used to store relationships, properties and data nodes.
Q. Is it possible to fragment a graph in Neo4j?
It is quite difficult to fragment a graph on Neo4j.
Q. Neo4j Vs MongoDB?
|Primary database model is Graph DBMS.||Primary database model is Document Store.|
|Implemented in Java and Scala.||Impleted in C++ Langauage.|
|Neo4j has 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|
Q. Explain how can we delete/create databases in Neo4j?
Just remove the whole graph directory using rm -rf, as Neo4j is not storing anything outside that:
rm -rf data/*
Q. Neo4J written in which language?
Neo4J is written Java and Scala.
Q. Which query language does Neo4j uses?
Neo4j uses CQL (Cypher Query Language).
Q. Can we fragment a Neo4J graph easily across multiple servers?
No, Its not so easy to fragment a Neo4J graph across multiple servers, as the data is made directly from the related.
Q. Brief Neo4j CQL LIMIT clause?
For filtering or limiting the number of rows that return by a query, we use Neo4j CQL LIMIT clause.
Q. Explain what is Neo4j?
Neo4j - An open-source NoSQL graph database management system that developed by Neo4j, Inc.
Q. What does property type value mean in Cypher?
- The Cypher Query is able to return property type values.
- These types of values are used as a parameter.
- These property types of values can be stored as properties and they can are constructed with the help of Cypher literals.
- The property type values consist of Numbers which are both float and integer type and it also consists of strings and booleans.
Q. What do you mean by structural types values in Cypher?
- Another type of value in Cypher is the Structural type.
- The Cypher Query can return this type of values.
- These values will not be able to use parameters.
- The structural type values cannot be stored in form of properties and also they cannot be constructed with Cypher literals.
- The structural value types are comprised of nodes, relationships, and paths.
Q. What is the IN Operator syntax?
IN Operator Syntax: IN[ ]
Q. CREATE UNIQUE is used for?
CREATE UNIQUE used for fixing the graph structures.
Q. Why is it useful to label nodes of graph database?
In case of Neo4j, it is very useful to label the nodes of the graph databases since it helps in attaching one or many simple types of nodes and relationships. It will also help in mentioning the role of a node which may be specific or general and also used to add Metadata like index and constraints. Labels are used for grouping nodes into sets and the nodes that are with the same label will belong to the same set.
Q. What is the type of cypher language, declarative language or procedural language?
Cypher language is considered to be a declarative language. Declarative language will allow the users to decide what data need to be retrieved and their performance is more general. Cypher will provide you with a declarative way so that you can query the graph.
Q. Which is fastest to handle graphs, MYSQL or Neo4j?
To handle graphs Neo4j is the fastest one compared to MYSQL.
Q. Mention the advantages of using Neo4j.
1. Neo4j is considered to be a native graph database which is build keeping in mind certain aspects like traversing of nodes and relationships, storage and also optimization of fast management.
2. Neo4j is compatible with the whiteboard. For the purpose of design, conception, storage and visualization for any use case or any domain, the property graph method will make sure that the user will be able to use the same model.
3. The Cypher language used in Neo4j and it is useful since it represents graphs and relationships in a visual manner.
4. Rapid development of also supported by Neo4j.
5. True data safety is provided by Neo4j since it follows ACID based transactions.
Q. What do you mean by Composite types of values?
- The composite type is of values are used as a parameter.
- These values can be created with the help of Cypher literals
- They can be fetched from Cypher queries.
- These values cannot be stored as properties.
- The composite type of values comprises of lists and maps.
Q. Mention the reading clauses in Cypher Query language.
The clauses that are used for reading data from the database are known as Reading Clauses.
1. Match - it is used specify the pattern for the purpose of searching in the Cypher Query database.
2. Optimal match - it is also used to mention the patterns that are to be searched for in the database and it also uses the null option to mention the unmatched pattern.
3. Start - through the legacy indexes, this start clause of use of finding the start point.
Q. What do you mean by projecting clauses?
In order to return to the set of result, the clause that is used to define the expression is known as projecting clause.
1. Return - it is used to determine what is needed to be returned in the result query set.
2. Unwind - it is utilized for expanding a list into a row that too in a form of a sequence.
Q. Which architecture allows for remote server?
REST architecture, that allows neo4j for remote servers.