How to generate a diagram of a very large database schema (SQL Server)

Question

I have a very large database I need to diagram. The database is SQL Server 2008 on x64. It is large in that there are hundreds of related tables, each with up to 2000 fields (some are sparse), multiple relationships between tables (often hundreds per table, in fact), multiple schemas... you get the idea.

I tried to use the Database Diagrams feature of SQL Server Management Studio, but it crashed with a Win32Exception: "Not enough storage is available to process this command..."

I tried to use Visio's reverse engineering feature on a different machine to connect in and diagram it, but that's been going for a few hours with no sign of completion.

The scripts to build this giant schema are being by a tool we built for the job. While the tool is doing its job just fine, it's tricky to visualise its output.

I'm after a tool to kick out a diagram of this database so we can do this. Any suggestions?

EDIT: Just to emphasize, the diagram is indeed not supposed to be used for actual useful reference. It's a client relationship management device to demonstrate the complexity/scale of the system.

Answer 1

I worked at a place that had several hundred tables (near 1k) and no one really knew what was going on in the system, company was growing and hiring a lot. A guy was tasked with doing a diagram, and he auto-magically created a gigantic tiled poster that contained every table with lines connecting various tables (going all over the place). I'm not sure what he used, it was Unix and Oracle years ago (way before Linux and open source). There was no real rhyme or reason to the layout of the the tables in his diagram. He had successfully created a diagram of every table. The "poster" was put on a wall in a common area, and got a few looks, but no one ever really used it, it was unusable, too cluttered, too unorganized. As a result, I used MS-Word to create a single page diagram containing the 20 main tables (it went through a few iterations as I "discovered" new main tables) with lines for each foreign key and each table located in a logical manner. I showed the column name, data type, nullability, PK, and all FKs. I put my diagram up on my wall by my monitor. Eventually everyone wanted a copy of my diagram, including the person that made the "poster". When I left that job they were still giving my diagram to new hires.

I recommend that you work like an explorer, find the key tables and map them as you go, making as many specific diagrams as necessary as you discover the system. Trying to make a gigantic "poster" automatically will not work very well.

Answer 2

Generating an image of any kind for a database of that size simply becomes eye candy that is stuck on a wall that draw's gasps, and honestly serves no real purpose except occasional glances. Why not use a tool like Red Gate's Documentation tool that will serve an actual purpose? Please understand I'm not saying this in a mocking way, but I've been down this road before trying to diagram a huge database, and I succeeded to some degree, but never found a good outlet where it was of some use.

Answer 3

Since you have multiple schemas maybe a good idea is to generate diagrams per schema instead