An ERDPlus alternative — when the schema already exists
ErdDocs is the alternative for a database that already exists: paste the dump below and the ER diagram plus a data dictionary are generated in your browser — PostgreSQL, MySQL, Prisma, DBML and six more formats in; PNG, SVG, Mermaid, DBML, PlantUML and SQL out. ERDPlus is a free academic modeling tool, and at its own job — designing a schema by drawing it, then converting the drawing into a relational schema and SQL — it is genuinely good. The reverse direction is the one it was never built for: there is no SQL import, so an existing database means redrawing every table by hand.
Side by side, honestly
| ERDPlus | ErdDocs | |
|---|---|---|
| Built for | Designing a schema from scratch, by hand | Documenting a schema that already exists |
| How the diagram appears | You draw it: entities, attributes, cardinalities | Generated from a pasted SQL dump or ORM schema |
| SQL | Output: generated from the drawn diagram | Input: ten formats read as-is; SQL also exported |
| Notations | Chen and crow’s foot; weak entities, attribute types | Crow’s foot only — the physical schema shape |
| When the schema changes | Re-draw the affected entities | Paste the new dump; regenerated in seconds |
| Where your schema goes | Saved in an account on ERDPlus servers | Nowhere — parsed locally, never uploaded |
| Beyond the diagram | Relational and star schema conversions | A printable data dictionary; PNG, SVG, Mermaid, DBML, PlantUML and SQL exports |
| Pricing | Completely free | 25 tables drawn in full and a three-table dictionary preview, free without an account; $9 once, forever, for everything beyond |
ERDPlus is a trademark of its owner; the comparison reflects public product information as of August 2026.
When ERDPlus is the right call
Coursework, and any schema that exists only in your head. Chen notation with weak entities and attribute ovals is how database design is taught, drawing each cardinality yourself is how it is learned, the ER-to-relational conversion ERDPlus performs is the exact skill the exam tests, and all of it is free. ErdDocs is free without an account too — up to 25 tables, and no sign-up before the first diagram.
When it stops fitting
The moment the schema lives in a database instead of a drawing. Migrations change tables weekly; a drawn diagram goes stale the first week nobody re-draws it. From a dump, regeneration costs seconds — and the same parse produces the data dictionary that coursework never asks for but every handover does.
A school management schema — the kind ERDPlus assignments describe — generated from SQL, not drawn. Replace it with your own dump; nothing is uploaded.
FAQ
What is a good ERDPlus alternative for a database that already exists?
ErdDocs. Paste a SQL dump, a Prisma schema or ORM models and it generates the ER diagram and a data dictionary in the browser — free for schemas up to 25 tables, no account. ERDPlus itself has no SQL import, so for an existing database every table would have to be redrawn by hand.
Is ErdDocs a replacement for ERDPlus in a database course?
For the design half, no — and ErdDocs takes over exactly where that half ends: when the schema exists as SQL and the diagram should come from it, not from memory. The drawing is the assignment itself: ERDPlus makes you place every entity and choose every cardinality yourself — Chen notation, weak entities, the conversion to a relational schema — and that deliberate practice is the point of the assignment. Once the tables are real, pasting the dump gives the diagram in seconds, and the same parse produces the data dictionary a handover needs.
Can ERDPlus import an existing SQL schema?
No — ERDPlus generates SQL from diagrams you draw, but does not parse SQL into a diagram. That one-way street is the reason this page exists: with an existing database you would redraw every table by hand. ErdDocs reads the dump directly — PostgreSQL, MySQL, Prisma, DBML and six more formats.
Both tools are free — what is the actual difference?
The direction of work. In ERDPlus the diagram is the source and SQL is the output. In ErdDocs the schema is the source, and the diagram plus a data dictionary are the output. ERDPlus stores diagrams in an account on its servers; ErdDocs parses in the browser with no account at all: schemas up to 25 tables are drawn in full, with a three-table preview of the dictionary, and unlocking the rest is one payment, not a subscription.
Does ErdDocs draw Chen notation with weak entities and attribute ovals?
No — ErdDocs draws crow’s foot only, because that is the shape a physical schema has: tables, columns, keys, and cardinality read straight off the foreign keys. Chen diamonds, multi-valued attributes and weak-entity double borders belong to the design stage, and ERDPlus draws those. For a database that already exists, crow’s foot is the notation the diagram is meant to be in, and ErdDocs produces it from the dump with no decisions to make.
Related
- School management system ER diagram — the full example above, with the modeling decisions explained.
- Crow’s foot notation — the reading rules ERDPlus assignments expect you to know.
- Lucidchart alternative · Dataedo alternative — the same honest comparison for two other tools.