Tuesday, June 26, 2012

There is a way to represent the schema of a database in text. Of course a diagram is very helpful in visualing the relationships, but you can also write out the schema if you have to. Suppose we have the following from the Access Relationship Designer. It is a diagram of one of the simple databases we use in class. The purpose of the database is to record hours worked by employees in a factory on various work orders.

We can represent this in text with a few conventions: bold for a required field, italic for foreign key and underline for primary key. List the table name and then the field names in parentheses.This yields the text schema below.

Employees(empno, fname, lname, rate, mgrno)
Labor(empno, wono, start, end, hours)

Note the composite primary key in the labor table. Each column is also a foreign key.

You might find this technique useful if dashing off a quick Email or you are without your favorite drawing tools.

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