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Neo4j - CQL General Clauses

Neo4j - CQL General Clauses

作者: 韩维思 | 来源:发表于2018-11-22 19:38 被阅读0次

    1. Return Clause

    1.1 Returning Single Node

    Create (node:label {properties}) 
    RETURN node
    

    1.2 Returning Multiple Nodes

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

    1.3 Returning Relationships

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

    eg.

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

    1.4 Returning Properties

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

    eg.

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

    1.5 Returning All Elements

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

    1.6 Returning a Variable With a Column Alias

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

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

    2. Order By Clause

    2.1 Simple Order By

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

    eg.

    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"})
    
    MATCH (n)  
    RETURN n.name, n.runs 
    ORDER BY n.runs 
    
    Order by Result

    2.2 Ordering Nodes by Multiple Properties

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

    eg.

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

    2.3 Ordering Nodes by Descending Order

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

    3. Limit Clause

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

    3.1

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

    eg.

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

    3.2 Limit with expression

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

    4. Skip

    4.1 Skip

    Returns all the nodes in the database skipping the first 3 nodes.

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

    4.2 Skip Using Expression

    You can skip the records of a result using an expression.

    MATCH (n)  
    RETURN n.name, n.runs 
    ORDER BY n.runs DESC 
    SKIP toInt (2*rand())+ 1 
    

    5. With Clause

    You can chain the query arts together using the WITH clause.

    MATCH (n) 
    WITH n 
    ORDER BY n.property 
    RETURN collect(n.property) 
    

    eg.

    MATCH (n) 
    WITH n 
    ORDER BY n.name DESC LIMIT 3 
    RETURN collect(n.name) 
    
    With

    6. Unwind Clause

    Following is a sample Cypher Query which unwinds a list. --拆解一个collection

    UNWIND ['a', 'b', 'c', 'd'] AS x 
    RETURN x 
    
    image.png

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