A data model is a "road map" that describes the data objects in a schema. It shows what tables are in the schema, some information about the columns in those tables, and some information about the relationships between the tables. There are several graphic representations for data models.
IDE1FX is one of the most mature, and certainly most full featured graphical data model representations. IDE1FX is part of a family of graphic models for all kinds of program and process information. There are two common levels of display used by IDE1FX: the logical model which concentrates on getting the tables and columns correctly enumerated and the "high level" relationships between tables defined, and the physical model which delves more deeply into how the tables and relationships are actually implemented using a particular database engine.
"Crows foot" is another data modeling notation. It can be used by many of the popular data modeling tools.
Many of the high-end development environments include a data modeling tool. Microsoft's Visual Studio Enterprise and Rational's Rose come right to my mind. I've been surprised by the number of developers and consultants that have these tools, but don't realize it!
If you don't already have one, be prepared for "sticker shock" when you check out database modeling tools. Computer Associate's ErWin is the granddaddy of data modeling tools, and Sybase's PowerDesigner is well respected too. Microsoft's Visio Professional is one of the lowest cost data modeling tools that I'd recommend, at around US$500 MSRP (note that it will NOT generate scripts for you, but it will reverse engineer and model nicely).
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This was first published in September 2002