ER Diagram Best Practices

An ER diagram review is not a casual glance at the diagram before implementation. It is a systematic quality assurance process that validates the model against multiple criteria: correctness, completeness, clarity, consistency, and conformance to standards.

Without a structured approach, reviews become informal 'looks good to me' exercises that miss errors. These errors then propagate into the physical schema, application code, and production data—where they become exponentially more expensive to fix.

This page presents a comprehensive Review Checklist that you can apply to any ER diagram. The checklist is organized into phases that mirror the aspects of quality we've covered throughout this module. Each phase contains specific validation points with criteria for pass/fail assessment.

Using This Checklist

The checklist is designed for systematic application:

1. Pre-Review Preparation: Gather materials; understand context
2. Structured Review: Work through each section methodically
3. Issue Documentation: Record findings with severity and recommendations
4. Resolution Tracking: Follow up on identified issues

Before examining the diagram itself, gather the materials and context needed for an effective review.

Materials to Collect

Context Questions to Answer

1. What is the purpose of this model? (New system design? Extension to existing? Migration?)
2. What is the scope? (Entire enterprise? Single application? Specific domain?)
3. Who are the intended audiences? (Developers? Business analysts? DBAs?)
4. What level of abstraction? (Conceptual? Logical? Physical?)
5. What standards apply? (Organizational naming conventions? Industry standards?)

Review Team Configuration

For significant models, involve multiple perspectives:

Scheduling Considerations

• Allow adequate time: 1-2 hours for small models; half-day or more for large ones
• Review when fresh—avoid end-of-day fatigue for critical reviews
• Schedule follow-up for issue resolution

Review each entity in the model against these criteria:

For each entity, review its attributes:

Special Attention: Key Attributes

Review each relationship in the model:

Review the diagram as a visual artifact:

The Squint Test Revisited

After detailed review, step back and look at the overall structure:

• Can you identify the central entities at a glance?
• Do clusters and groupings make sense?
• Does the layout suggest hierarchy or flow?
• Does it feel organized or chaotic?

If the gestalt impression is confusion, layout improvements are needed—even if all details pass individually.

Verify that documentation supports the diagram:

The model must accurately represent business reality:

Scenario Walk-Through Technique

For each major business process, walk through the model:

1. Narrate the process: 'A customer calls to place an order.'
2. Trace entities involved: Customer → Order → OrderLine → Product
3. Verify relationships: Customer places Order; Order contains OrderLine; OrderLine references Product
4. Check cardinality: Customer can have many Orders; Order must have at least one OrderLine
5. Validate constraints: Order must have Customer (total participation); OrderLine quantity must be positive

If the walk-through encounters gaps or contradictions, the model needs revision.

When review identifies issues, document and track them systematically.

Issue Severity Classification

Review Meeting Structure

For formal reviews, structure the meeting:

1. Opening (5 min): Confirm scope, introduce participants, set expectations
2. Overview (10 min): Modeler presents high-level structure
3. Detailed Review (varies): Walk through checklist systematically
4. Issue Discussion (10-20 min): Prioritize and assign issues
5. Closing (5 min): Summarize findings; confirm next steps

Post-Review Follow-Up

1. Distribute review findings within 24 hours
2. Modeler addresses issues and documents resolutions
3. Re-review if critical/high issues require significant changes
4. Final sign-off when all critical/high issues resolved

For convenient reference, here is a consolidated view of all checklist categories:

Customizing the Checklist

This checklist is comprehensive but may need adaptation for your organization:

• Add organization-specific standards (naming conventions, required metadata)
• Adjust severity thresholds based on project risk tolerance
• Include compliance-specific checks (GDPR, HIPAA, industry regulations)
• Tailor for model type (conceptual vs. logical vs. physical)
• Add automation where possible (naming pattern validators, documentation completeness checks)

A systematic review process transforms ER diagram quality from dependent on individual skill to reliably achieved through process. The checklist ensures that reviews are thorough, consistent, and effective.

Module Complete

With this page, you have completed the ER Diagram Best Practices module. You now have a comprehensive foundation in naming conventions, diagram layout, documentation practices, common mistake recognition, and systematic review processes.

These practices separate professional-quality data modeling from ad hoc diagram creation. Applied consistently, they yield ER diagrams that communicate clearly, implement correctly, and remain maintainable over time.

Applying What You've Learned

Practice is essential. Apply these principles to:

• Review existing diagrams in your organization
• Create or refine your organization's ER diagram standards
• Conduct formal reviews using the checklist
• Mentor others in best practices

The transition from knowing best practices to habitually applying them comes through deliberate practice.