Connect the Tables: How to Graph Relational Databases

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Photo by Shannon Potter on Unsplash Jennifer Reif Developer Advocate, Neo4j [email protected] @JMHReif github.com/JMHReif jmhreif.com linkedin.com/in/jmhreif Connect the Tables: How to Graph Relational Databases

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Who is Jennifer Reif? Developer Advocate, Neo4j • Continuous learner • Conference speaker • Creator: Tech blogger + podcaster • Other: geek Jennifer Reif [email protected] @JMHReif github.com/JMHReif jmhreif.com linkedin.com/in/jmhreif

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Data set

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Kaggle - public data Co ff ee Shop https://www.kaggle.com/datasets/ylchang/co ff ee-shop-sample-data-1113 https://github.com/JMHReif/graphing-relational-dbs-data-import/tree/main Cleaned —>>

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Demo 1 - Look at CSVs Live! • customer.csv • order.csv • product.csv • sales_outlet.csv • sta ff .csv • product_type.csv

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Demo 1 - Model it Live! https://arrows.app

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Relational

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Data set sample (core entities) Order Product Customer Building Sta f

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Data Normalization 3rd Normal Form (3NF) • Unique row, low data duplication • Primary key or composite key (where necessary) • Foreign keys to link tables • Many-to-many relationships -> JOIN tables • JOINs on query-time, from expert knowledge https://dzone.com/articles/do-we-need-data-normalization-anymore

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Relational ERD Co ff ee Shop

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Graph

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What is a graph? Connected data • Store relationships -> separate entities • JOINs on write, not read • Flexible schema • Query language: Cypher

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Still get core features No FOMO here :) • Physical storage • Transactional + analytical workloads • ACID transactions • Indexes / constraints • Security features • Cloud hosting • Free -> enterprise solutions

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Graph components Graph theory foundations • Node (vertex) • Relationship (edge)

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Nodes Graph components • Represent objects or entities • Can be labeled • May have properties Order Product Employee orderId: 162468 orderDate: 2019-04-01 productId: 08746589 name: “Ipoh Coffee” id: 247924 startDate: 2016-05-04 position: “Barista”

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Relationships Graph components • Must have a type • Must have a direction • May have properties • Nodes can have multiple Order Product Employee orderId: 162468 orderDate: 2019-04-01 productId: 08746589 name: “Ipoh Coffee” id: 247924 startDate: 2016-05-04 position: “Barista” CONTAINS date: 2022-08-16 tip: 1.00 SOLD CONTACT CREATED

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Label Graph components • A group of nodes • Like a category Person Employee Customer

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Property Graph components • Key-value pair • Associated with node or relationship • Like a variable name and value Order Employee orderId: 162468 id: 247924 SOLD orderDate: 2019-04-01 date: 2022-08-16 tip: 1.00 startDate: 2016-05-04 position: “Barista”

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Naming conventions Relational vs Graph • Recommendations vary! • Lowercase • Separator: _ • Avoid keywords • Capitalize SQL keywords • Might change with GQL standard • camelCase • UPPERCASE • Separator: _ • Avoid keywords • Capitalize Cypher keywords https://brainstation.io/learn/sql/naming-conventions https://neo4j.com/docs/cypher-manual/current/syntax/naming/ SQL Cypher

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Demo 2 - Translate the model

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Relational -> Graph Data model • Tables -> Labels • Row = Node • FK = Relationship • JOIN table = Relationship

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• Tables = Labels • Row = Node • FK = Relationship • JOIN table = Relationship https://arrows.app

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• Tables = Labels • Row = Node • FK = Relationship • JOIN table = Relationship

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• Relationship direction • Type/Name • No right or wrong! • Sensible for your model

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Modeling decisions

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What to do… When things are not cut and dry? • Property on node or relationship? • Promo • Property or node? • Line item • More than 1 label? • Seasonal drink

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- Every data modeler ever “It depends…”

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Tips and Tricks General architecture • De fi ne use case -> • Know what problem you’re solving • Outline key queries -> • Optimize model to answer those • Limitations are di ff erent • More entities <> bad • Model can change as-needed

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Tips and Tricks General practices • Frequent fi lter -> • Opt for separate node/rel • Props with few/unchanging values -> • Consider label • Dense nodes (hypernodes) -> • Consider more relationship types to fi lter

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Data export / import

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MariaDB Export / Import • SQL dump fi le (entire db) • SQL statement to CSV

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Neo4j Export / Import • Cypher + APOC • ETL Tool • Dump fi le (beware)

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Other options for both Export + Import + Sync • Driver • Messaging platform • Scheduled task

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Demo 3 - Import to Neo4j

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Setup Load components • Neo4j Docker container • Shell script -> cypher-shell • Cypher script • LOAD CSV

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Draft data model = real-world model Recap!

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Draft = Graph model Co ff ee Shop

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All or nothing?

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Polyglot Graphy data -> graph db • Store data with complicated JOINs in a graph • E.g. Customer -> Order -> Product • Eval: • JOINs • Frequency • Performance criticality

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Cypher

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Cypher • Functional and visual • Based on ASCII-art • Declarative query language • Focuses on what to retrieve • Not how A B LIKES MATCH (A)-[:LIKES]->(B)

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Cypher: powerful and expressive Jennifer Neo4j WORKS_FOR CREATE (:Person { name: ‘Jennifer’}) -[:WORKS_FOR]-> (:Company { name: ‘Neo4j’}) NODE PROPERTY NODE PROPERTY LABEL LABEL

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Cypher: read Jennifer Neo4j WORKS_FOR MATCH (:Person { name: ‘Jennifer’} ) -[:WORKS_FOR]-> ( whom ) RETURN whom

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Translating queries • SELECT • Property list • FROM • JOIN ON • WHERE • GROUP BY • HAVING • MATCH • RETURN entities/props • Pattern (node)-[rel]-(node2) • -[var:REL_TYPE]-> • WHERE • Implicit in RETURN • WHERE on aggregations SQL Cypher

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Demo 4 - SQL vs Cypher

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Refactoring

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Relational vs Graph Designed di ff erently • DDL / DML • Strict schema + data types • Structure-enforced • Data integrity • Storage/query optimization • Changes = dependency impacts • Schema- fl exible • Restrictions set as-needed • Governance-enforced • Data integrity • Storage/query optimization • Changes = less cascading impacts Relational Graph

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This means… Refactoring for graphs • Streamlined • Faster • More responsive • Less invasive

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Tools For refactoring • Cypher + APOC • Neo4j Migrations (https://neo4j.com/labs/neo4j-migrations/) • 3rd party tools (Kettle, etc)

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But wait…there’s more!

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https://dev.neo4j.com/nodes24

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Resources Questions? • Github repo: github.com/JMHReif/connect-the-tables • Modeling (Arrows): arrows.app • SQL / Cypher: neo4j.com/docs/getting-started/cypher-intro/cypher-sql/ • GraphAcademy: graphacademy.neo4j.com/ Jennifer Reif Developer Advocate, Neo4j [email protected] @JMHReif github.com/JMHReif jmhreif.com linkedin.com/in/jmhreif