Freeware is a plus. Could you also describe with one sentence why it should be good enough for occasional usage?
Edit: You might check this cool link , providing more info about entity relationship diagrams and tools
Edit: For the chosen answer couple of tips - click on entity even it looks like circle and type the name and Enter - it will give you the Entity box - Click on association , Ctrl + L would give you the nice line
You can use StarUML with the ER extension. It is totally free, stable and easy to learn.
Update: 09.10.2017: StarUML is not free anymore!
Dbdesigner 4 at http://www.fabforce.net/dbdesigner4/downloads.php. It's free, easy to use, does reverse engineering.
yEd is a powerful desktop application that can be used to quickly and effectively generate high-quality diagrams for free.
http://www.yworks.com/en/products_yed_about.html
MySQL Workbench is also excellent
Oracle Data Modeling - works with Oracle, MsSQL and DB2
MySQL Workbench - works with MySQL
In case you are using Visual Studio - it has it's own diagram tool integrated. Works good enough for me.
Try Dezign for Databases. It's very easy to use (but powerful enough for most development tasks, supports a wide range of databases and finally the price (~245 $) is not that much. Personally I'm very happy with the tool.
Toad Data Modeler - costs 400 USD, but is worth the price. Currently it offers many nice features, and they are still adding more. There is an excellent user community around this tool, and it is quite easy to stay in touch with development team.
SQL Power Architect Community Edition at http://www.sqlpower.ca/page/architect_download_os. A friend of mine used it for a project and said it was easy, reasonably powerful, and free.
I've said this in another answer but I have two more suggestions:
1) No-one seems to have mentioned the great tool which my uni recommends. Its a 620K download called ER-Assistant. Its basic plain black/white ERD's but some like that. Its free and uses Crows foot notation, but windows only.
http://highered.mcgraw-hill.com/sites/0072942207/student_view0/e_r_assistant.html
2) Also Lucid Charts is decent. Its free to use until you reach very complex diagrams. Its web based so obviously platform agnostic https://www.lucidchart.com
来源：https://stackoverflow.com/questions/857488/recommendation-for-a-good-entity-relationship-diagram-building-tool-for-occasion