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Neo4j Graph Database Fundamentals · レッスン

グラフデータの更新と削除

SETとREMOVEを使って既存のノードとリレーションシップを変更し、DELETEとDETACH DELETEでデータを安全に削除する方法を学びます。

「グラフデータの更新と削除」はCoddyKit上の無料Neo4j Graph Database Fundamentalsレッスンです。 これはレッスン3/4です。 下記で完全なレッスンを無料で読むことができます。その後、ブラウザ内の組み込みコードエディタと24時間対応のAIチューターでハンズオン演習できます。 これはNeo4j Graph Database Fundamentals学習パスの一部であり、ウェブとCoddyKitアプリ全体で進捗が同期されます。 Neo4j Graph Database Fundamentalsコースには全4レッスンが含まれています。

このレッスンの一部はまだ翻訳されておらず、英語で表示されています。

Modifying Your Graph Data

In this lesson, you'll learn how to update and delete existing nodes and relationships in your Neo4j graph using Cypher. Modifying data is crucial for keeping your graph accurate and up-to-date.

We'll cover the essential clauses: SET for changing properties, REMOVE for taking properties or labels away, and DELETE / DETACH DELETE for removing graph elements entirely.

Update Node Properties with SET

The SET clause is used to modify existing properties on nodes or relationships, or to add new ones. Let's start by updating a node's property.

This example first creates a 'Person' node, then updates their age.

CREATE (p:Person {name: 'Alice', age: 30})
RETURN p

MATCH (p:Person {name: 'Alice'})
SET p.age = 31
RETURN p.name, p.age

Update Relationship Properties

Just like nodes, relationships can also have properties. You can use SET to update these properties too. First, we create a relationship, then we update one of its properties.

CREATE (p1:Person {name: 'Bob'})-[:KNOWS {since: 2019}]->(p2:Person {name: 'Charlie'})
RETURN p1, p2

MATCH (p1:Person {name: 'Bob'})-[r:KNOWS]->(p2:Person {name: 'Charlie'})
SET r.since = 2020, r.status = 'Good Friends'
RETURN r.since, r.status

Add New Properties with SET

If you use SET with a property name that doesn't exist on a node or relationship, Cypher will simply add that new property. This is a handy way to extend your data model on the fly.

MATCH (p:Person {name: 'Alice'})
SET p.city = 'New York', p.occupation = 'Engineer'
RETURN p.name, p.city, p.occupation

Remove Properties with REMOVE

Sometimes you need to get rid of a property entirely. The REMOVE clause is designed for this. It can delete one or more properties from a node or a relationship.

Remember, REMOVE is for properties and labels, not for deleting entire nodes or relationships.

MATCH (p:Person {name: 'Alice'})
REMOVE p.occupation
RETURN p.name, p.age, p.city, p.occupation

Remove Node Labels

The REMOVE clause isn't just for properties; you can also use it to remove labels from a node. This can change the node's type or classification within your graph.

After removing the 'Person' label, the node still exists but is now just a generic node without that specific type.

MATCH (p:Person {name: 'Alice'})
REMOVE p:Person
RETURN p, labels(p)

Delete Relationships with DELETE

To remove a relationship, you use the DELETE clause. You must first MATCH the relationship you want to delete and then pass its variable to DELETE.

Note: DELETE can only remove relationships or nodes that have no relationships.

CREATE (a:User {id: 1})-[:LIKES]->(b:Product {id: 10})
RETURN a, b

MATCH (a:User {id: 1})-[r:LIKES]->(b:Product {id: 10})
DELETE r
RETURN a, b

Delete Nodes with DETACH DELETE

What if you want to delete a node that has relationships connected to it? A simple DELETE won't work and will give an error.

The solution is DETACH DELETE. This powerful clause deletes the node and all its incoming and outgoing relationships in one go.

CREATE (u:User {name: 'David'})-[:FOLLOWS]->(o:User {name: 'Eve'})
RETURN u, o

MATCH (u:User {name: 'David'})
DETACH DELETE u
RETURN u

Deletion Best Practices

Deleting data is permanent! Always exercise caution:

  • Test first: Run your MATCH clause with a RETURN to ensure you're selecting the correct elements before adding DELETE or DETACH DELETE.
  • Backup: For critical data, ensure you have backups.
  • Transaction awareness: In applications, deletions are often part of larger transactions.

Deletion Challenge

You have a (:Movie {title: 'Inception'}) node that is connected to many (:Actor) nodes via [:ACTED_IN] relationships. You want to remove the 'Inception' movie node and all its connections.

Lesson Summary

Great job! You've mastered the core Cypher clauses for modifying and deleting graph data:

  • SET: Updates existing properties or adds new ones to nodes and relationships.
  • REMOVE: Deletes specific properties or labels from nodes and relationships.
  • DELETE: Removes relationships or nodes that have no connections.
  • DETACH DELETE: The safest way to delete a node and all its associated relationships in one go.

Always be careful when deleting data, and verify your MATCH patterns first!

よくある質問

「グラフデータの更新と削除」レッスンは無料ですか？

はい。「グラフデータの更新と削除」の完全なテキストはこのウェブで無料で読めます。インタラクティブに演習し（組み込みコードエディタと24時間対応のAIチューター）、Neo4j Graph Database Fundamentalsコースの残りをアンロックするには、CoddyKit PROにアップグレードしてください。 Neo4j Graph Database Fundamentalsコースには全4レッスンが含まれています。

「グラフデータの更新と削除」で何を学びますか？

SETとREMOVEを使って既存のノードとリレーションシップを変更し、DELETEとDETACH DELETEでデータを安全に削除する方法を学びます。 ブラウザで直接実行するハンズオンコードでNeo4j Graph Database Fundamentalsを演習し、24時間対応のAIチューターがレッスンを進める中での質問に答えます。

Neo4j Graph Database Fundamentalsを始めるのに経験は必要ですか？

事前経験は必要ありません。CoddyKitのNeo4j Graph Database Fundamentalsは初級者から上級者向けに構成されているため、ここから始めるか最初から始めて、自分のペースで進むことができます。 これはレッスン3/4です。

「グラフデータの更新と削除」レッスンにはどのくらい時間がかかりますか？

ほとんどのCoddyKitレッスンは約5～10分かかります。各レッスンはコンパクトでインタラクティブなので、着実に進歩し、ウェブとアプリ全体で正確に前回の場所から再開できます。

このNeo4j Graph Database Fundamentalsレッスンでコードを書いて実行できますか？

はい。すべてのNeo4j Graph Database Fundamentalsレッスンに組み込みコードエディタが含まれているため、ブラウザでリアルコードを書いて実行し、即座のAIフィードバックを取得できます。ローカル設定は不要です。

このコースのすべてのレッスン

  1. 結果のフィルタリングと並べ替え
  2. 集計とプロジェクション
  3. グラフデータの更新と削除
  4. WITHとUNIONによるクエリの結合
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