Like SQL, Neo4j CQL has provided some aggregation functions to use in RETURN clause. It is similar to GROUP BY clause in SQL.

We can use this RETURN + Aggregation Functions in MATCH command to work on a group of nodes and return some aggregated value.

AGGREGATION Functions List

Following is the list of aggregation functions in Neo4j.

The limit clause is used to limit the number of rows in the output.

Syntax

Following is the syntax of the LIMIT clause.

MATCH (n)
RETURN n
ORDER BY n.name
LIMIT 3

Example

Before proceeding with the example, create 5 nodes in the Neo4j database as shown below.

CREATE(Dhawan:player{name:"shikar Dhawan", YOB: 1985, runs:363, country: "India"})
CREATE(Jonathan:player{name:"Jonathan Trott", YOB:1981, runs:229, country:"South Africa"})
CREATE(Sangakkara:player{name:"Kumar Sangakkara", YOB:1977, runs:222, country:"Srilanka"})
CREATE(Rohit:player{name:"Rohit Sharma", YOB: 1987, runs:177, country:"India"})
CREATE(Virat:player{name:"Virat Kohli", YOB: 1988, runs:176, country:"India"})

Following is a sample Cypher Query which returns the nodes created above in a descending order and limits the records in the result to 3.

MATCH (n)
RETURN n.name, n.runs
ORDER BY n.runs DESC
LIMIT 3

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Limit with expression

You can also use the LIMIT clause with expression.

Example

Following is a sample Cypher Query which limits the records using an expression.

MATCH (n)
RETURN n.name, n.runs
ORDER BY n.runs DESC
LIMIT toInt(3 * rand())+ 1

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Assume we have created a graph in the database with the following details.

Count

The count() function is used to count the number of rows.

Syntax

Following is the syntax of the count function.

MATCH (n { name: ''A'' })-->(x)
RETURN n, count(*)

Example

Following is a sample Cypher Query which demonstrates the usage of the count() function.

Match(n{name: "India", result: "Winners"})--(x)
RETURN n, count(*)

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Group Count

The COUNT clause is also used to count the groups of relationship types.

Example

Following is a sample Cypher Query which counts and returns the number of nodes participating in each relation.

Match(n{name: "India", result: "Winners"})-[r]-(x)
RETURN type (r), count(*)

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Like SQL, Neo4j CQL has provided WHERE clause in CQL MATCH command to filter the results of a MATCH Query.

Syntax

Following is the syntax of the WHERE clause.

MATCH (label)
WHERE label.country = "property"
RETURN label

Example

Before proceeding with the example, create five nodes in the database as shown below.

CREATE(Dhawan:player{name:"shikar Dhawan", YOB: 1985, runs:363, country: "India"}
CREATE(Jonathan:player{name:"Jonathan Trott", YOB:1981, runs:229, country:"South Africa"}
CREATE(Sangakkara:player{name:"Kumar Sangakkara", YOB:1977, runs:222,
   country:"Srilanka"})
CREATE(Rohit:player{name:"Rohit Sharma", YOB: 1987, runs:177, country:"India"})
CREATE(Virat:player{name:"Virat Kohli", YOB: 1988, runs:176, country:"India"})
CREATE(Ind:Country {name: "India", result: "Winners"})

Following is a sample Cypher Query which returns all the players (nodes) that belongs to the country India using WHERE clause.

MATCH (player)
WHERE player.country = "India"
RETURN player

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

WHERE Clause with Multiple Conditions

You can also use the WHERE clause to verify multiple conditions.

Syntax

Following is the syntax to use WHERE clause in Neo4j with multiple conditions.

MATCH (emp:Employee)
WHERE emp.name = ''Abc'' AND emp.name = ''Xyz''
RETURN emp

Example

Following is a sample Cypher Query which filters the nodes in the Neo4j database using two conditions.

MATCH (player)
WHERE player.country = "India" AND player.runs >=175
RETURN player

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Using Relationship with Where Clause

You can also use Where clause to filter the nodes using the relationships.

Example

Assume we have the following graph in the database.

Following is a sample Cypher Query to retrieve the top scorer of India using WHERE clause as shown below.

MATCH (n)
WHERE (n)-[: TOP_SCORER_OF]->( {name: "India", result: "Winners"})
RETURN n

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result. Here you can observe that Neo4j returned the node, which has the relation TOP_SCORER_OF to the country with the node having the name India.

You can arrange the result data in order using the ORDER BY clause.

Syntax

Following is the syntax of the ORDER BY clause.

MATCH (n)
RETURN n.property1, n.property2 . . . . . . . .
ORDER BY n.property

Example

Before proceeding with the example, create 5 nodes in Neo4j database as shown below.

CREATE(Dhawan:player{name:"shikar Dhawan", YOB: 1985, runs:363, country: "India"})
CREATE(Jonathan:player{name:"Jonathan Trott", YOB:1981, runs:229, country:"South Africa"})
CREATE(Sangakkara:player{name:"Kumar Sangakkara", YOB:1977, runs:222, country:"Srilanka"})
CREATE(Rohit:player{name:"Rohit Sharma", YOB: 1987, runs:177, country:"India"})
CREATE(Virat:player{name:"Virat Kohli", YOB: 1988, runs:176, country:"India"})

Following is a sample Cypher Query which returns the above created nodes in the order of the runs scored by the player using the ORDERBY clause.

MATCH (n)
RETURN n.name, n.runs
ORDER BY n.runs

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Ordering Nodes by Multiple Properties

You can arrange the nodes based on multiple properties using ORDEYBY clause.

Syntax

Following is the syntax to arrange nodes by multiple properties using the ORDERBY clause.

MATCH (n)
RETURN n
ORDER BY n.age, n.name

Example

Following is a sample Cypher Query which arranges the nodes created earlier in this chapter based on the properties – runs and country.

MATCH (n)
RETURN n.name, n.runs, n.country
ORDER BY n.runs, n.country

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Ordering Nodes by Descending Order

You can arrange the nodes in a database in a descending order using the ORDERBY clause.

Syntax

Following is the syntax to arrange the nodes in a database.

MATCH (n)
RETURN n
ORDER BY n.name DESC

Example

Following is a sample Cypher Query which arranges the nodes in a database in a descending order using the ORDERBY clause.

MATCH (n)
RETURN n.name, n.runs
ORDER BY n.runs DESC

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

The RETURN clause is used return nodes, relationships, and properties in Neo4j. In this chapter, we are going to learn how to −

• Return nodes
• Return multiple nodes
• Return relationships
• Return properties
• Return all elements
• Return a variable with column alias

Returning Nodes

You can return a node using the RETURN clause.

Syntax

Following is a syntax to return nodes using the RETURN clause.

Create (node:label {properties})
RETURN node

Example

Before proceeding with the example, create 3 nodes and 2 relationships as shown below.

Create (Dhoni:player {name: "MahendraSingh Dhoni", YOB: 1981, POB: "Ranchi"})
CREATE (Ind:Country {name: "India", result: "Winners"})
CREATE (CT2013:Tornament {name: "ICC Champions Trophy 2013"})
CREATE (Ind)-[r1:WINNERS_OF {NRR:0.938 ,pts:6}]->(CT2013)
CREATE(Dhoni)-[r2:CAPTAIN_OF]->(Ind)

Following is a sample Cypher Query which creates a node named Dhoni and returns it.

Create (Dhoni:player {name: "MahendraSingh Dhoni", YOB: 1981, POB: "Ranchi"})
RETURN Dhoni

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Returning Multiple Nodes

You can also return multiple nodes using the return clause.

Syntax

Following is the syntax to return multiple nodes using the return clause.

CREATE (Ind:Country {name: "India", result: "Winners"})
CREATE (CT2013:Tornament {name: "ICC Champions Trophy 2013"})
RETURN Ind, CT2013

Example

Following is a sample Cypher Query to return multiple nodes using the return clause.

CREATE (Ind:Country {name: "India", result: "Winners"})
CREATE (CT2013:Tornament {name: "ICC Champions Trophy 2013"})
RETURN Ind, CT2013

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result. Here you can observe that Neo4j returned 2 nodes.

Returning Relationships

You can also return relationships using the Return clause.

Syntax

Following is the syntax to return relationships using the RETURN clause.

CREATE (node1)-[Relationship:Relationship_type]->(node2)
RETURN Relationship

Example

Following is a sample Cypher Query which creates two relationships and returns them.

CREATE (Ind)-[r1:WINNERS_OF {NRR:0.938 ,pts:6}]->(CT2013)
CREATE(Dhoni)-[r2:CAPTAIN_OF]->(Ind)
RETURN r1, r2

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Returning Properties

You can also return properties using the RETURN clause.

Syntax

Following is a syntax to return properties using the RETURN clause.

Match (node:label {properties . . . . . . . . . . })
Return node.property

Example

Following is a sample Cypher Query to return the properties of a node.

Match (Dhoni:player {name: "MahendraSingh Dhoni", YOB: 1981, POB: "Ranchi"})
Return Dhoni.name, Dhoni.POB

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Returning All Elements

You can return all the elements in the Neo4j database using the RETURN clause.

Example

Following is an example Cypher Query to return all the elements in the database.

Match p = (n {name: "India", result: "Winners"})-[r]-(x)
RETURN *

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Returning a Variable With a Column Alias

You can return a particular column with alias using RETURN clause in Neo4j.

Example

Following is a sample Cypher Query which returns the column POB as Place Of Birth.

Match (Dhoni:player {name: "MahendraSingh Dhoni", YOB: 1981, POB: "Ranchi"})
Return Dhoni.POB as Place Of Birth

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

The FOREACH clause is used to update data within a list whether components of a path, or result of aggregation.

Syntax

Following is the syntax of the FOREACH clause.

MATCH p = (start node)-[*]->(end node)
WHERE start.node = "node_name" AND end.node = "node_name"
FOREACH (n IN nodes(p)| SET n.marked = TRUE)

Example

Before proceeding with the example, create a path p in Neo4j database as shown below.

CREATE p = (Dhawan {name:"Shikar Dhawan"})-[:TOPSCORRER_OF]->(Ind{name:
   "India"})-[:WINNER_OF]->(CT2013{name: "Champions Trophy 2013"})
RETURN p

Following is a sample Cypher Query which adds a property to all the nodes along the path using the FOREACH clause.

MATCH p = (Dhawan)-[*]->(CT2013)
   WHERE Dhawan.name = "Shikar Dhawan" AND CT2013.name = "Champions Trophy 2013"
FOREACH (n IN nodes(p)| SET n.marked = TRUE)

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Verification

To verify the creation of the node, type and execute the following query in the dollar prompt.

MATCH (n) RETURN n

This query returns all the nodes in the database (we will discuss this query in detail in the coming chapters).

On executing, this query shows the created node as shown in the following screenshot.

In this chapter, we will learn about Match Clause and all the functions that can be performed using this clause.

Get All Nodes Using Match

Using the MATCH clause of Neo4j you can retrieve all nodes in the Neo4j database.

Example

Before proceeding with the example, create 3 nodes and 2 relationships as shown below.

CREATE (Dhoni:player {name: "MahendraSingh Dhoni", YOB: 1981, POB: "Ranchi"})
CREATE (Ind:Country {name: "India", result: "Winners"})
CREATE (CT2013:Tornament {name: "ICC Champions Trophy 2013"})
CREATE (Ind)-[r1:WINNERS_OF {NRR:0.938 ,pts:6}]->(CT2013)

CREATE(Dhoni)-[r2:CAPTAIN_OF]->(Ind)
CREATE (Dhawan:player{name: "shikar Dhawan", YOB: 1995, POB: "Delhi"})
CREATE (Jadeja:player {name: "Ravindra Jadeja", YOB: 1988, POB: "NavagamGhed"})

CREATE (Dhawan)-[:TOP_SCORER_OF {Runs:363}]->(Ind)
CREATE (Jadeja)-[:HIGHEST_WICKET_TAKER_OF {Wickets:12}]->(Ind)

Following is the query which returns all the nodes in Neo4j database.

MATCH (n) RETURN n

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Getting All Nodes Under a Specific Label

Using match clause, you can get all the nodes under a specific label.

Syntax

Following is the syntax to get all the nodes under a specific label.

MATCH (node:label)
RETURN node

Example

Following is a sample Cypher Query, which returns all the nodes in the database under the label player.

MATCH (n:player)
RETURN n

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Match by Relationship

You can retrieve nodes based on relationship using the MATCH clause.

Syntax

Following is the syntax of retrieving nodes based on the relationship using the MATCH clause.

MATCH (node:label)<-[: Relationship]-(n)
RETURN n

Example

Following is a sample Cypher Query to retrieve nodes based on relationship using the MATCH clause.

MATCH (Ind:Country {name: "India", result: "Winners"})<-[: TOP_SCORER_OF]-(n)
RETURN n.name

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

Delete All Nodes

You can delete all the nodes using the MATCH clause.

Query

Following is the query to delete all the nodes in Neo4j.

MATCH (n) detach delete n

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result.

The OPTIONAL MATCH clause is used to search for the pattern described in it, while using nulls for missing parts of the pattern.

OPTIONAL MATCH is similar to the match clause, the only difference being it returns null as a result of the missing parts of the pattern.

Syntax

Following is the syntax of the OPTIONAL MATCH with relationship.

MATCH (node:label {properties. . . . . . . . . . . . . .})
OPTIONAL MATCH (node)-->(x)
RETURN x

Example

Following is a sample Cypher Query which tries to retrieve the relations from the node ICCT2013. Since there are no such nodes, it returns null.

MATCH (a:Tornament {name: "ICC Champions Trophy 2013"})
OPTIONAL MATCH (a)-->(x)
RETURN x

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result. Here you can observe that since there are no matches for the required pattern, Neo4j returned null.

You can delete nodes and relationships from a database using the DELETE clause.

Deleting All Nodes and Relationships

Following is the query to delete all the nodes and the relationships in the database using the DELETE clause.

Query

MATCH (n) DETACH DELETE n

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

This will delete all the nodes and relationships from your neo4j database and make it empty.

Deleting a Particular Node

To delete a particular node, you need to specify the details of the node in the place of “n” in the above query.

Syntax

Following is the syntax to delete a particular node from Neo4j using the DELETE clause.

MATCH (node:label {properties . . . . . . . . . .  })
DETACH DELETE node

Example

Before proceeding with the example, create a node “Ishant” in the Neo4j database as shown below.

CREATE (Ishant:player {name: "Ishant Sharma", YOB: 1988, POB: "Delhi"})

Following is a sample Cypher Query which deletes the above created node using the DELETE clause.

MATCH (Ishant:player {name: "Ishant Sharma", YOB: 1988, POB: "Delhi"})
DETACH DELETE Ishant

To execute the above query, carry out the following steps −

Step 1 − Open the Neo4j desktop App and start the Neo4j Server. Open the built-in browser app of Neo4j using the URL http://localhost:7474/ as shown in the following screenshot.

Step 2 − Copy and paste the desired query in the dollar prompt and press the play button (to execute the query) highlighted in the following screenshot.

Result

On executing, you will get the following result. Here you can observe that the specified node is deleted.