ER Diagram Generator
Create entity-relationship diagrams from your data model
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Can you name every foreign key in the database you shipped last year? Most teams cannot, because the diagram that would answer it was never drawn, or it went stale two migrations ago. ER Diagram Generator gives that map back. Describe the tables and how they connect, and the entities, keys and relationships come back written out.
Short answer: ER Diagram Generator is a free AI tool that turns a written description of your tables into an entity relationship model, naming every entity, its key fields and how each one relates to the others, cardinality included.
What is ER Diagram Generator?
ER Diagram Generator is a database tool on EizTools that builds an entity relationship model from a description you write. List your tables, the fields that matter and the links between them, and a structured model of the whole thing comes back.
That model is text, not a picture file, which suits the job: a written list of entities, keys and cardinality is what goes into a design doc or a pull request. ER Diagram Generator reads nothing from your live database, so anything left out of your description is missing from the model.
Three Teams, Three Different Diagrams
The same tool covers jobs that look nothing alike.
| Who is asking | What they paste in | What the model gives them |
|---|---|---|
| Developer who inherited a billing schema | Exported CREATE TABLE statements | A relationship map before touching a migration |
| Product manager in sprint planning | A description of orders, shipments and returns | Settles whether one order can have many shipments |
| Student writing up a library project | Rules for members, copies and loans | Entities and cardinality for the report |
A freelancer quoting a clinic booking build runs it before the estimate, to see how many tables patients, appointments and invoices really need.
How Does ER Diagram Generator Work?
Paste or type the description, then open advanced options, where two settings decide what comes back. Set Output Type to ER Diagram, because that shared panel also lists Query, Migration and Index Plan. Set Format to Table for a compact entity list, or Explained when you want the reasoning behind each relationship.
Format also offers SQL. A diagram is not a script, so leave that value to the tools that write DDL. When you do want the CREATE TABLE statements afterwards, take the agreed entity list over to SQL Generator.
Database sets the engine your field types match. Complexity starts on Standard, and Add Constraints and Include Indexes are already on, so keys appear without asking.
Note Run the same description twice, once with Complexity on Simple and once on Advanced. The gap between the two is usually where an unclear relationship hides.
Describing Your Data So The Relationships Land Right
The model is only as good as the sentence describing each link. Five habits make the difference.
- Name entities in the singular: customer, invoice, invoice line.
- Put numbers in the relationship, for example one invoice has many lines.
- Flag the optional links. A shipment that can exist without an order changes the model.
- Name the join tables you already have, or new ones get invented for you.
- Paste real DDL when you have it. Column names and types beat a summary every time.
What works well
- Turns a vague planning conversation into a concrete entity list
- Catches the many to many links people forget, such as students and courses
- Maps an undocumented schema from pasted DDL, with no database connection involved
What to watch for
- Text you read or paste, not an image ready for a slide
- It knows only what you wrote, so a table you forgot never appears
- Cardinality is a suggestion until you check it against real rows
Free AI tools sit at the centre of EizTools, each built for a single job and open without an account. You choose the AI model from the selector before you generate, and the rest of the coding tools pick up where this one stops, from writing the schema to debugging the query.
Frequently Asked Questions
Does it produce an image I can drop into a slide?
No. The result is text: an entity list, the key fields and the link between each pair. You can ask in Custom Instructions for a text diagram format, then paste that into your own drawing tool.
Can it read my existing database?
Not directly, because nothing here connects to a server. Export your CREATE TABLE statements and paste them in instead. A model built from real DDL beats one built from memory every time.
Does the engine I pick change the model?
Yes, in the field types. Set Database to the engine you build on, PostgreSQL or MySQL, and the model uses types you can actually create. Relationships and cardinality stay the same either way.
How many tables can I describe at once?
About a dozen entities stays readable in one pass. Past that, split the description by area, generate each part on its own, then join the models yourself so nothing quietly gets summarised away.
A schema argument that runs twenty minutes usually ends the moment somebody writes the entities down. Describe your tables in the box above, then take the corrected model into the build.
Sabir Bepari
Founder of EizTools and a passionate AI enthusiast dedicated to building practical, user-friendly AI tools that simplify everyday tasks.
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