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wbd-entity-relationship-diagrams

Teaches drawing ER diagrams with crow's foot notation across three relational schema walkthroughs.

2|Updated Jun 1, 2026
Search Tags:#data modeling#database schema#er diagram#cardinality#whiteboarding#junction table#crow's foot notation
One-click install
npx skills add https://github.com/jay-steenbergen/MSSAMentorAgent --skill wbd-entity-relationship-diagrams-jay-steenbergen
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: wbd-entity-relationship-diagrams
Source: https://github.com/jay-steenbergen/MSSAMentorAgent/tree/main/.github/skills/tracks/whiteboarding/wbd-entity-relationship-diagrams
Command: npx skills add https://github.com/jay-steenbergen/MSSAMentorAgent --skill wbd-entity-relationship-diagrams-jay-steenbergen

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve? Learners who can write SQL often cannot communicate a data model visually before writing migrations, leading to schema mistakes discovered too late. This Skill teaches how to draw entity-relationship diagrams using crow's foot notation so schema design decisions are visible and reviewable before any CREATE TABLE statement. ## Core Features & Use Cases - Crow's Foot Cardinality Drills: Practice one-to-one, one-to-many, and many-to-many relationships, including the rule that many-to-many always requires a junction table. - Three Guided Schema Walkthroughs: Draw an e-commerce model (8 entities), a blog with tags (composite-key junction), and a multi-tenant SaaS model with a structured review exercise. - ER Review Discipline: Learn to interrogate a diagram for missing junctions, missing tenant isolation, referential integrity gaps, and unmodeled cascade rules. - Use Case: A learner preparing to design a database for a project sketches the full schema on a whiteboard in under 10 minutes, then reviews it with a teammate to catch design gaps before writing migrations. ## Quick Start Ask the mentor to start the ER diagram whiteboarding project and walk you through drawing an e-commerce schema with crow's foot notation.

Frequently Asked Questions about wbd-entity-relationship-diagrams

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I draw an ER diagram with crow's foot notation?▼

Draw each entity as a rectangle with its name in singular uppercase, list attributes inside, and mark the primary key. Connect entities with lines whose end symbols show cardinality: bars mean exactly one, circles mean optional, and crow's feet mean many.

How do I model a many-to-many relationship in a relational database?▼

Many-to-many relationships always require a junction table whose rows are pairs of foreign keys, such as ENROLLMENT(student_id, course_id). Junction tables typically use a composite primary key and can carry their own attributes like a role column.

What is the difference between one-to-many and many-to-many in ER diagrams?▼

One-to-many means each parent row relates to many children but each child belongs to exactly one parent, like a user and their orders. Many-to-many means both sides can have many of the other, which cannot be stored directly and requires a junction table.

Does this cover Chen notation or PlantUML diagrams?▼

No, the scope is limited to crow's foot notation, which covers the majority of ER usage in working teams. Chen's diamond notation, DBML, and PlantUML class diagrams are explicitly out of scope.

How do I review someone else's ER diagram for design gaps?▼

Ask targeted questions: are junction tables present for every many-to-many, does every tenant-scoped table carry a tenant_id, are cascade and deletion rules decided, and are referential integrity constraints like assignee membership enforced. The diagram becomes the review agenda.

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