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Category: neo4j
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Khóa học miễn phí Neo4j – Count Function nhận dự án làm có lương
Neo4j – Count Function
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.
Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc
Khóa học miễn phí Neo4j – Limit Clause nhận dự án làm có lương
Neo4j – Limit Clause
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.
Khóa học lập trình tại Toidayhoc vừa học vừa làm dự án vừa nhận lương: Khóa học lập trình nhận lương tại trung tâm Toidayhoc
