Database Design and ER Diagrams - Database Cheat Sheet

How a design becomes a database: crow's foot diagrams, entities and keys, one to one, one to many and many to many, and must or may. Each rule is shown with SQLite enforcing it.

On the sheet:

- Reading a crow's foot diagram: the four symbols and a clinic diagram

- Diagram words: what each one becomes in a table

- An entity becomes a table: CREATE TABLE and its structure

- One to many, many to many: where the key goes, and junction tables

- One to one: the key that is also the link

- Keys: candidate, primary and alternate

- Must or may: participation, with SQLite enforcing it

- Attributes and entities: five kinds of attribute, strong and weak

- Six marks of good data: accuracy to relevance

Two A4 pages, printed front and back, sized to print once and keep beside you while you work. Written in short sentences and plain English, for readers whose first language is not English and clearer for everyone else because of it.

It pairs with the Why Health Data Needs a Home, Reading the Blueprint: ER Diagrams and Logical Data Modeling books, so you can learn each idea in full and then revise it here in two pages.

Every query on this sheet was run against a live database before the page was printed, so the result you read is the result you get. Instant PDF download. By M.R. Sterling.