ERD Builder guide

Think in entities, then draw the rules

ERD Builder is a visual workspace for conceptual Chen and EER diagrams. Start with business objects and their relationships, before deciding how they become SQL tables.

You build the model with shapes and connectors. There is no SQL or text syntax to paste into the Builder; the modeling plan below is a checklist you can follow on the canvas.

Build your first model

1. Open ERD Builder and choose a sample or an empty ERD. Add Entity shapes from the Shapes library by clicking, tapping, dragging, or pressing Enter or Space.
2. Create Customer and Order. Double-click a label to rename it, or use the Inspector. Select each entity and use Build from selection to attach key attributes and ordinary attributes.
3. Create the places Relationship and connect it to Customer and Order. Select the connectors to set cardinality, participation, and role names.
4. Review Model checks, then use Arrange and Fit view to make the model readable. Use Undo if an edit or arrangement needs to be reversed.

Entity Customer
  Key attribute: customer_id
  Attribute: name

Entity Order
  Key attribute: order_id
  Attribute: ordered_at

Relationship places
  Customer: 0..N orders per customer
  Order: 1..1 customer per order

Chen symbols & attribute notation

Cardinality & participation

Classic cardinality accepts 1, N, M, or *. Min-max cardinality uses a non-negative integer minimum and an integer, N, M, or * maximum. Apply a valid range with Enter or by leaving the field; Escape cancels a pending edit.

Use partial participation when an instance may take part in no relationship occurrence, and total participation when it must participate. State optionality deliberately instead of guessing from a connector’s position.

Give repeated participation distinct role names, for example employee and manager in a self relationship. An Annotation only connection is visual context and does not contribute to semantic model checks.

Customer places Order
  Business rule: one customer can place many orders.
  Each order belongs to exactly one customer.
  Customer participation: partial (a customer may have no orders).
  Order participation: total (an order must have a customer).

EER roles & model checks

For an ISA specialization, choose one Supertype (parent) and at least one Subtype (child) on the connectors. Set disjoint or overlapping membership and partial or total coverage on the ISA shape. Moving or arranging shapes preserves these explicit roles.

For a union category, assign at least two distinct Union member entities and one distinct Resulting subtype. Use aggregation to represent a relationship group as a higher-level modeling concept.

Model checks flag issues such as missing roles, invalid endpoints, unsafe ownership, and inheritance cycles. No issues found means the current structural checks pass; it does not validate instance data or prove every business rule.

Arrange, focus & edit efficiently

Arrange offers Smart, Chen, horizontal, vertical, radial, organic, compact-tree, and grid layouts. Lock a shape’s position when arrangements should preserve it. Drag connector bends and labels to improve readability without changing semantic roles.

Use Find a shape in the Inspector or a Model checks entry to reveal and focus a target. Attributes and Focus create temporary views; Diagram view settings can enable attribute-count badges. These view choices do not change the saved model or undo history.

Undo/Redo works through the toolbar and Ctrl/Cmd+Z, Ctrl/Cmd+Y, or Ctrl/Cmd+Shift+Z. Selection tools support duplicate, delete, alignment, and distribution. Ctrl/Cmd+C/V copies and pastes a selection through the current workspace’s in-memory Builder clipboard.

Double-click a shape label to edit it. Enter adds a line; Ctrl/Cmd+Enter or leaving the field commits, and Escape cancels. On a narrow screen, use Shapes and Inspector to open panels; compact Undo/Redo controls remain on the canvas.

Convert, export, save & share

1. Choose Convert ERD to SQL, then select SQLite, PostgreSQL, MySQL, or SQL Server. Review the relational tables, keys, constraints, and column types.
2. Resolve missing cardinalities, one-to-one foreign-key holders, and other mapping choices. Review conversion notes for rules needing application logic or triggers; confirm them after completing the mapping.
3. Choose Open in SQL to ERD to load the generated SQL in a new SQL editor document. Save Builder changes before leaving when you want to keep the conceptual model.
4. Use Export diagram for PNG, image-backed SVG, or PDF, capturing the current view or entire diagram. Sign in to save an editable Builder file and share its saved read-only public view.

How a conceptual model maps to SQL

The SQL review validates final table/key sizes as well as model structure. MySQL output targets 8.0.16+ with utf8mb4, DYNAMIC rows, and 16 KB InnoDB pages; SQL Server output targets 2016+. Check the selected database profile before using the generated DDL.

Conversion reads the complete model, including temporarily hidden attributes. Mapping choices in the review do not silently edit the saved conceptual diagram. A loaded public diagram can be converted into a new SQL document while the original remains read-only.

Troubleshoot a Builder model

Turn an AI answer into a modeling plan

Use Copy AI Prompt to give an assistant this guide, then add your business requirements. Ask for entities, identifiers, attributes, relationship rules, and any unresolved questions.

Review the answer and create the shapes on the canvas. Keep unknown cardinalities explicit until you can confirm them. Use the SQL conversion review when you are ready for a physical schema.

Design a Chen model for a library. List entities, key attributes,
relationships, endpoint min-max cardinalities, and participation.
Ask about unknown business rules before deciding them.
Return a modeling checklist for Erd Go ERD Builder.