Neo4j 数据导入案例NorthWind load csv

妖狐艹你老母 2022-04-08 11:09 417阅读 0赞

介绍如何从关系数据库,以csv的文件格式，导入数据到neo4j数据库。重点理解关系数据库和图形数据库建模的联系。

## 一、 Northwind 数据库介绍 ##

社区版本的数据样例，主要用来练习sql语句的查询。有较为丰富的表结构和复杂的 关联关系。  
![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2tvdXJ5b3VzaGluZQ_size_16_color_FFFFFF_t_70]  
**两个核心思想**

*  列row代表一个节点node
 *  一个表table代表一个标签lable

## 二、数据导入 ##

### 1，load csv命令导入数据 ###

> dbms.directories.import=import 配置文件该参数表示load csv的默认访问路径在import文件夹下面  
> 参考：neo4j server\\neo4j-community-3.5.0\\import  
> [点击csv文件下载链接][csv]

下载后把数据放在import文件夹下,执行以下命令创建角色节点

// Create customers
    USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/customers.csv" AS row
    CREATE (:Customer {companyName: row.CompanyName, customerID: row.CustomerID, fax: row.Fax, phone: row.Phone});
    
    // Create products
    USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/products.csv" AS row
    CREATE (:Product {productName: row.ProductName, productID: row.ProductID, unitPrice: toFloat(row.UnitPrice)});
    
    // Create suppliers
    USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/suppliers.csv" AS row
    CREATE (:Supplier {companyName: row.CompanyName, supplierID: row.SupplierID});
    
    // Create employees
    USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/employees.csv" AS row
    CREATE (:Employee {employeeID:row.EmployeeID,  firstName: row.FirstName, lastName: row.LastName, title: row.Title});
    
    // Create categories
    USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/categories.csv" AS row
    CREATE (:Category {categoryID: row.CategoryID, categoryName: row.CategoryName, description: row.Description});
    
    USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/orders.csv" AS row
    MERGE (order:Order {orderID: row.OrderID}) ON CREATE SET order.shipName =  row.ShipName;

**解释：**

1.  periodic commit 指示Neo4j在执行完一定行数后提交数据再继续，默认执行1000行,即每1000行提交一次
2.  WITH HEADERS 表示input文件第一行是header，而不是数据。可以用header的字段选择插入
3.  AS row，row是标识符代表了一列。 row.header字段名代表字段值，可以给属性动态赋值。  
    总结：请理解一行数据代表一个节点，一个表文件代表一个角色label。

### 2、 建立索引 ###

通过上面语句建立了大量的彼此之间毫无联系的节点。为了加快建立关系速度，给所有节点加上索引。

CREATE INDEX ON :Product(productID);
    CREATE INDEX ON :Product(productName);
    CREATE INDEX ON :Category(categoryID);
    CREATE INDEX ON :Employee(employeeID);
    CREATE INDEX ON :Supplier(supplierID);
    CREATE INDEX ON :Customer(customerID);
    CREATE INDEX ON :Customer(customerName);
    #以在NODE或关系的属性上创建唯一约束。
    CREATE CONSTRAINT ON (o:Order) ASSERT o.orderID IS UNIQUE;

### 3 创建节点间关系 ###

#### 3.1 建立order和product，customer,employee关系 ####

USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/orders.csv" AS row
    MATCH (order:Order {orderID: row.OrderID})
    MATCH (product:Product {productID: row.ProductID})
    MERGE (order)-[pu:PRODUCT]->(product)
    ON CREATE SET pu.unitPrice = toFloat(row.UnitPrice), pu.quantity = toFloat(row.Quantity);
    
    USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/orders.csv" AS row
    MATCH (order:Order {orderID: row.OrderID})
    MATCH (employee:Employee {employeeID: row.EmployeeID})
    MERGE (employee)-[:SOLD]->(order);
    
    USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/orders.csv" AS row
    MATCH (order:Order {orderID: row.OrderID})
    MATCH (customer:Customer {customerID: row.CustomerID})
    MERGE (customer)-[:PURCHASED]->(order);

**解释**

1.  加载order文件，找到order和product的所有节点。这里的match不是匹配而是查找的意思
2.  创建order和product的关系为PRODUCT
3.  SET 设置属性，为关系设置属性  
    ![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2tvdXJ5b3VzaGluZQ_size_16_color_FFFFFF_t_70 1]

#### 3.2 创建products, suppliers，categories的关系 ####

USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/products.csv" AS row
    MATCH (product:Product {productID: row.ProductID})
    MATCH (supplier:Supplier {supplierID: row.SupplierID})
    MERGE (supplier)-[:SUPPLIES]->(product);
    
    USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/products.csv" AS row
    MATCH (product:Product {productID: row.ProductID})
    MATCH (category:Category {categoryID: row.CategoryID})
    MERGE (product)-[:PART_OF]->(category);

#### 3.3 创建员工和管理者的关系 ####

USING PERIODIC COMMIT
    LOAD CSV WITH HEADERS FROM "file:/employees.csv" AS row
    MATCH (employee:Employee {employeeID: row.EmployeeID})
    MATCH (manager:Employee {employeeID: row.ReportsTo})
    MERGE (employee)-[:REPORTS_TO]->(manager);

表中两列的关系

### 结果查询 ###

#### 1，返回员工和经理报告层级 ####

match (employee:Employee) -[:REPORTS_TO]-> (manager:Employee) return employee,manager

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2tvdXJ5b3VzaGluZQ_size_16_color_FFFFFF_t_70 2]

#### 2，找到所有卖过巧克力的人以及销量 ####

match(employee:Employee ) -[:SOLD]->(ord:Order) -[:PRODUCT]-> (product:Product {productName:"Chocolade"})  return employee.firstName,count ( ord) AS ords

## 总结 ##

1.  以上可以看出关系型数据库和图形数据库是如何转化的。但个人不推荐使用图形数据库来做上述查询，我们都很清楚关系型数据库可以很轻松达成如上功能。随着业务复杂度的提高，图形数据库使用起来会越来越复杂。二关系型数据库可以对业务拆解，有更好的效率。
2.  图形数据库适合处理关系相关的业务逻辑
3.  重点是通过这个案例理解图形数据库如何建立模型和处理数据的。

[官网参考，适合喜欢英语阅读的人][Link 1]

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[csv]: https://github.com/neo4j-contrib/developer-resources
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2tvdXJ5b3VzaGluZQ_size_16_color_FFFFFF_t_70 1]: /images/20220405/6a086d0f50864026af8608fa0edd8a56.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2tvdXJ5b3VzaGluZQ_size_16_color_FFFFFF_t_70 2]: /images/20220405/410387ced12e4ffaab53dd7755c47eac.png
[Link 1]: https://neo4j.com/developer/guide-importing-data-and-etl/