SQLite Schema Diagram Generator

https://gitlab.com/Screwtapello/sqlite-schema-diagram

by tempodox • 2 years ago

523 87 2 years ago

idoubtit• 2 years ago

I remember writing a script for doing this, more than 10 years ago. I haven't used it much, and not for many years.

The problem is that a fully automatic schema is only readable for very small databases. So small that very soon you can keep the structure in your head. For larger databases, the automatic schema will be awful. Even with just 20 tables, graphviz (dot | neato) will make a mess when some tables are referenced everywhere (think of `created_by` and `updated_by` pointing to `user_id`).

When I need a map of a large database, I usually create a few specialized diagrams with dbeaver, then combine them into a PDF file. Each diagram is a careful selection of tables.

olejorgenb• 2 years ago

Regardless, the implementation in 128 lines of SQL combined with graphviz is cool.

vidarh2• 2 years ago

And the sql is mostly comments. The actual SQL is ~50 lines with plenty of whitespace.

alexvoda3• 2 years ago

As with all such tools the issue is the automatic layout algorithm.

I find that almost all layout algorithms for database diagrams are rather poor.

bbkane2• 2 years ago

You might try https://schemaspy.org/ - it generates a website with ER diagrams that only go one or two relationships out, but they have clickable table names to get to the next diagram

sbuttgereit• 2 years ago

ER diagrams that only go one or two relationships out

Actually, SchemaSpy gives you a full diagram of the entire schema as well: it gives it to you with a truncated columns list and a full columns list per table. The "Relationships" option at the top of the page is where the full diagram is accessed.

The one & two relations out limited views are if you're getting to the diagram from the scope of a specific table... it will show you one and two relations away from the current table when using that perspective. And, as you say, you can navigate the relationships that way.

What I really like about SchemaSpy (I use it with PostgreSQL) is that I can `COMMENT ON` database objects like tables and columns using markdown and SchemaSpy will render the Markdown in it's output. Simple markdown still looks decent when viewed from something like psql, too, so it's a nice way to have documentation carried with the database.

rplnt• 2 years ago

(offtopic warning)

A properly normalised database can wind up with a lot of small tables connected by a complex network of foreign key references

I think the last time I properly normalized a database was at a university. Avoidng lots of small tables and complex networks would be the main reason.

ThalesX2• 2 years ago

Huh. Just these days I’m building an MVP and was thinking that denormalized would probably be better. But I just can’t give normalization up.

petepete• 2 years ago

Don't. The benefits far outweigh the costs until you reach enormous scale.

lovasoa2• 2 years ago

You can do this a little bit easier using SQLPage [1], without GraphViz, and you'll get an always up to date schema:

    select 'table' as component, 'Foreign keys' as markdown;

    select *, (
      select
        group_concat(
          printf('[%s.%s](?table=%s)', fk."table",fk."to",fk."table"),
          ', '
      )
      from pragma_foreign_key_list($table) fk
      where col.name = fk."from"
    ) as "Foreign keys"
    from pragma_table_info($table) col;

[1] https://sql.ophir.dev (https://github.com/lovasoa/SQLpage#sqlpage)

vidarh2• 2 years ago

I don't see how this is in any way comparable - it looks like it'd just produces a table rather than a diagram? You can indeed do that too with a single sqlite query as well if it's not the diagram you want.

Nor how running some other tool that runs a web service qualifies as "easier" than running a query using sqlite itself, and a command line tool that's trivially scriptable.

lovasoa2• 2 years ago

Indeed, it's not the same thing, but it's comparable. This lets you quickly navigate the tables in your SQLite database.

littlecranky673• 2 years ago

Love this! 5mins after visiting the page it is built into my gitlab CI pipeline :)

gchaincl• 2 years ago

curious to know what are you using it for? do you upload a diagram on every push?

littlecranky673• 2 years ago

no, in my case only when the Migrations/ folder changes (you can specify that in .gitlab-ci.yml or using come commandline-fu). I'm using EF core as an ORM, thats why it is also easy to create an empty SQLite DB from the sources.

franga2000• 2 years ago

Thanks for the idea! I have a repo that (ab)uses Gitlab CI to periodically produce an SQLite database from a bunch of other data sources and this is a great addition to the README

littlecranky673• 2 years ago

Haha, I'm abusing gitlab pipeline minutes to run a periodical cypress task to test signup+login in production on my pet-project :) Scheduled pipelines for the win!

thristian11• 2 years ago

Author here, I didn't bother submitting this to HN because I figured it would be too niche and trivial to get much attention. Evidently I was wrong!

alexvoda3• 2 years ago

Really love that you used Kunth's "Literate programming" to document the code. You don't see it often but I find it really nice when seeing it.

vsnf• 2 years ago

It also adds a severe amount of visual clutter between the code. Individual preference I’m sure, but I’d prefer less comments, I think. Or maybe my IDE just needs to collapse comments inside functions automatically.

keepamovin• 2 years ago

This is very cool. Reminds me of my days 13 years ago using dot to draw complex planaarized graph diagrams before switching to physics / springs models, graph embeddings, and other cool things.

Nice to see a really good use for dot.

I created a fork on GitHub as a fork there'll be easier for me to come back to, find, organize and use (and may be for others too): https://github.com/o0101/sqlite-schema-diagram

I hope you don't mind? If you don't want ur code there let me know and I'll sadly but obediently take it down and just link to it from someplace on there I can readily find. :)

thristian11• 2 years ago

It's such a small script, most of the repository is documentation, so I expected (hoped) it would get copied to a lot of places. It's fine. :)

ncruces3• 2 years ago

I know this is terribly unfortunate, and supporting the monopoly, but consider a GitHub mirror.

I just mirrored it myself to keep tabs on it, because otherwise I'll forget it.

Very interesting approach.

vanous• 2 years ago

My opinion will probably not be popular, but by making the mirror you are helping with creating this monopoly.

I see the solution in creating small single/few page(s) landing site and linking to the code and releases, being it to self/hosted Gitea, Forgejo, Gitlab, GitHub...

thristian11• 2 years ago

Somebody upthread[1] also made a GitHub mirror. I appreciate that different people have different comfort-levels with the centralisation of services like GitHub, but luckily it's really easy for people to copy a Git repo to a host they're more comfortable with, like GitHub or SourceHut or even making a local clone.

[1] https://news.ycombinator.com/item?id=39800533

NortySpock• 2 years ago

Very nice, I've been doing some similar things at work to help map out a data warehouse migration project.

Have you considered outputting to a MermaidJS format?

https://mermaid.js.org/syntax/entityRelationshipDiagram.html

thristian11• 2 years ago

I have not considered outputting to MermaidJS, but (from a quick glance at that documentation) it looks like the same "SQL template" technique should work. Actually doing it is left as an exercise for the reader. :)

_ache_• 2 years ago

Thank you. Interesting little tool.

tejtm• 2 years ago

Likewise, the niche pressure for me came from SQLite being agnostic to a canonical form for SQL `.schema`. I did not need to get into parsing every flavor.

https://github.com/TomConlin/SQLiteViz

meitham• 2 years ago

The fact you achieved this with a query and graphiz is impressive! I wonder how much tweaks this query needs to make it work with DuckDB.

pjmlp• 2 years ago

I love that it is written in SQL, people keep forgeting it isn't only for queries.

Hendrikto2• 2 years ago

I was just looking for something like this. Ended up using DbVisualiser, which is far too heavy and complex for the simple task I wanted it for. This looks much neater.

abi• 2 years ago

Is there a similar one for Postgres? I’d love to use it.

Vuizur• 2 years ago

You can use DBeaver to get a good diagram for almost all RDBMs.

ccakes• 2 years ago

tbls[1] is a similar tool in this space that does a great job and is a simple single binary

Covers a lot of different platforms incl Postgres

[1] https://github.com/k1LoW/tbls

thristian11• 2 years ago

Years ago I wrote something similar for PostgreSQL. Unlike SQLite, it supports[1] the much richer "information_schema" database schema that's defined by the SQL standard. As long as you can figure out how it represents tables, columns, and primary and foreign keys, it shouldn't be too difficult to adapt this SQL query to fit. After all, reshaping relational data to extract the information you need is what SQL is for.

[1] https://www.postgresql.org/docs/current/information-schema.h...

dmfay• 2 years ago

My project pdot^1 has a full-ERD mode but it's honestly less useful than the semi-interactive/contextual mode of navigating schema subgraphs in a database of any size. pdot can output mermaid and render other graphs too, like trigger cascades and grant inheritance.

^1 https://gitlab.com/dmfay/pdot

gcanyon3• 2 years ago

I built a similar tool for my own use that:

1. Takes in a .dot file 2. Presents a simple UI for selecting which tables/relationships you want in the final diagram 3. Lets you highlight a table and add all directly related tables to the selected tables 4. Lets you select two tables and adds the tables for the shortest route between the tables 5. Lets you assign colors to tables/relationships for the final diagram 6. Optionally shows only key fields in the final diagram 7. Generates the necessary graph source and copies it to the clipboard, and loads either of two GraphViz pages to let you paste the source and see the graph.

If that would be of interest to anyone I'd be happy to post it.

codetrotter3• 2 years ago

I’d love to see it!

gcanyon3• 2 years ago

Okay, I'll package it up and post it.

willlma2• 2 years ago

Check out https://azimutt.app/

mrbuttons454• 2 years ago

Yes please!

gcanyon3• 2 years ago

Okay, I'll package it up and post it.

jll29• 2 years ago

This is a cool idea, I'm glad someone poasted it here.

However, SQLite3 on the Mac gave me:

  Error: near line 2: no such table: pragma_table_list

Somewhere it is written that pragma_table_list was only made available as of 3.16, but I am actually using

  sqlite --version
  3.35.4 2021-04-02 15:20:15 5d4c65779dab868b285519b19e4cf9d451d50c6048f06f653aa701ec212df45e

Anyone seen this?

codetrotter3• 2 years ago

Are you using SQLite that ships with macOS, or SQLite installed from homebrew?

I had a different problem in the past with the SQLite that ships with macOS, and have been using SQLite from homebrew since.

So if it’s the one that comes with macOS that gives you this problem that you are having, try using SQLite from homebrew instead.

https://brew.sh/

pmarreck• 2 years ago

run `which sqlite`

martinsnow• 2 years ago

Install a newer version

zoomablemind3• 2 years ago

Had this error with v3.33.

Does work with sqlite3 v3.40 and likely higher too.

thristian11• 2 years ago

Thanks for looking into it!

It turns out that 3.37.0 is the version that added the `table_list` pragma. I've added that requirement to the README.

thristian11• 2 years ago

I have not seen that, and that's very puzzling.

What output do you get when you run these commands?

    $ sqlite3 --version
    -- Loading resources from /home/st/.sqliterc
    3.45.1 2024-01-30 16:01:20 e876e51a0ed5c5b3126f52e532044363a014bc594cfefa87ffb5b82257ccalt1 (64-bit)
    $ sqlite3 :memory: -init /dev/null "select * from pragma_table_list();"
    -- Loading resources from /dev/null
    main|sqlite_schema|table|5|0|0
    temp|sqlite_temp_schema|table|5|0|0

EDIT: The ability to use pragmas as table-valued functions was added in version 3.16.0[1], but the table_list pragma was first added in 3.37.0[2], which is newer than your sqlite3 version.

[1] https://sqlite.org/changes.html#version_3_16_0

[2] https://sqlite.org/changes.html#version_3_37_0

bbkane2• 2 years ago

I love the diagram maker, and this looks like it has fewer dependencies than https://schemaspy.org/ (which is still FANTASTIC for larger databases).

tedivm• 2 years ago

Paracelsus creates diagrams in markdown or dot format for SQLAlchemy defined databases.

https://github.com/tedivm/paracelsus

andrewl• 2 years ago

This seems very clever. I’ve enjoyed abusing SQL, too. And note that abuse is the developer’s term for how what he’s doing in sqlite-schema-diagram.sql. I’m not trying to be insulting. I actually do like it.

chiph• 2 years ago

A place I worked at during the dot-com era had a large format printer[0] and the DBAs would occasionally print database schema diagram posters that they would hang on the walls. It was amazingly useful, especially as we staffed up and had a lot of new employees.

@thristian - can you specify a paper size?

[0] That once the marketing department found out about, was always out of ink.

thristian11• 2 years ago

So far as I can tell, GraphViz does not allow you to specify a paper size. However, if you render to SVG, you can open the result in Inkscape and rearrange things fairly easily. That's not quite as convenient as having it done automatically, but GraphViz can struggle with laying out a complex schema even when assuming infinite space - some amount of hand-tweaking is going to be necessary regardless.

yencabulator• 2 years ago

So far as I can tell, GraphViz does not allow you to specify a paper size.

Set the size of the graph in inches:

https://www.graphviz.org/docs/attrs/size/

eigenvalue• 2 years ago

Cool, I recently made a similar tool for generating diagrams like that for SQLalchemy data models. Can definitely be useful for understanding a complex schema.

KAKAN• 2 years ago

Such an awesome find, I'm thinking of sticking this to my CI Pipeline now! :D

I use SQLite for a gameserver, having 3 different databases for different stuff. And this would be a lifesaver for others working on anything requiring the main database which has a lot of relations, thanks to normalizing it and having a lot of different but related data. Thank you for this!

irreducible• 2 years ago

I built something similar for Prisma recently: https://github.com/irreducible-io/prisma2d2/

mingodad• 2 years ago

There is also https://github.com/ondras/wwwsqldesigner :

WWW SQL Designer, your online SQL diagramming tool

karmakaze• 2 years ago

I've used this in the past and is one of my first ways of approaching a new codebase. It's great at loading a schema and letting me lay out the tables. I'll sometimes make many different subset diagrams. I hacked it a bit for working with MySQL schema and inferring 'foreign keys' by naming convention as they are often not enforced by the db schema.

eloh• 2 years ago

Also checkout https://www.schemacrawler.com/

zoomablemind3• 2 years ago

Tried it on SQLite's own Fossil repo, which is a kind of SQLite db too.

The resulting diagram shows no relationship arrows.

Turns out the Fossil's schema uses REFERENCES clause with a table name only; I guess, this points to table's primary key by default. Apparently, the diagram generator requires explicit column names.

thristian11• 2 years ago

Huh. The syntax diagram in the documentation[1] suggests this is possible, but the documentation on foreign keys[2] does not mention that syntax, or how it's interpreted.

I think I can fix this.

[1] https://sqlite.org/syntax/foreign-key-clause.html

[2] https://sqlite.org/foreignkeys.html

thristian11• 2 years ago

I have pushed an update which should fix this issue.

zoomablemind3• 2 years ago

Just tested the fix on the Fossil's db. The arrows are displayed correctly. Thanks!

willlma2• 2 years ago

Lots of database management tools include some kind of schema diagram view, either automatically generated or manually editable so you can get the layout just right. But it's usually part of a much bigger suite of tools, and sometimes I don't want to install a tool, I just want to get a basic overview quickly.

An old colleague of mine created an interactive web app that does this. We use it internally and I find it super useful. Supports SQLite, among others: https://azimutt.app/

gmbuell2• 2 years ago

This seems really dangerous to use given it's AGPL license. IANAL but besides the inherent infectious nature of the .sql file itself, wouldn't the output .svg (or whatever) files that you produce by running this code _also_ be AGPL licensed?

teddyh2• 2 years ago

AGPL, nor any other GPL variant, does not cover the output of programs. Don’t fall for the FUD, and stop spreading it.

gmbuell2• 2 years ago

Google (as in, the corporation, not the search results) says anything derived from AGPL code may be covered by the AGPL license. It's enough of a threat that internal use of AGPL licensed tools is forbidden at both Google and Apple and probably others.

Source: https://opensource.google/documentation/reference/using/agpl...

wallymathieu• 2 years ago

I did something related to this https://github.com/wallymathieu/mejram Main reason I did it was that I've worked on some old databases that do not have a nice normalised schema. Some of the foreign keys have been missing. Using dot-render can give you nicer graphs compared to some of the built in tools like SQL Server Management Studio.

whartung• 2 years ago

What I like here is the "unix style do one thing" part of here's a simple ("simple") SQL script that pumps into GraphViz which does all of the heavy lifting.

aabbcc1241• 2 years ago

I made a similar FOSS [1] that can generate plain text erd from a live database, and also a visualizer based on the plain text.

It supports sqlite, mysql, mssql, postgres. And the visualizer is hosted on a CDN without login requirement.

[1] https://quick-erd.surge.sh

SQLite Schema Diagram Generator

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