First Guide to SQL Anywhere Studio
PART 2. Getting Results with SQL Anywhere Studio
CHAPTER 9. Designing Databases with SQL Modeler
The preceding tutorial introduces only the basic functionality of SQL Modeler. In fact, it is capable of handling the complete design or modification of your database schema, including all tables, views, indexes, references, triggers and procedures.
Other features greatly simplify the task of designing larger databases. For example, you can specify specific domains. A domain holds a particular type of data, such as a phone number. It has a data type associated with it, but is more specific. For example, you can create a domain of identification numbers. Whenever you need a identification number in a table, you can associate that column with the identification number domain. All properties and checks associated with that domain are attached automatically.
Domains reduce repetitive definitions. In doing so, they not only reduce your work, but also reduce the chance that you will erroneously use a different type definition or check procedure. Rather than identify a column as simply an integer, you specify what specific type of data that column contains. All instances of that data type share a common definition.
A business rule is a written expression of the way a business operates. For example, "the order shipped date must be greater than or equal to the order date" is a business rule.
Business rules fall into four categories:
Definition Expresses inherent properties of an object. Definitions typically describe entities.
Fact Expresses certainty or existence. Facts typically describe relationships.
Validation A constraint on a value.
Formula Calculation used to produce values.
Business rules are particularly handy because they relate directly to the task that a customer requires that a database perform. By recording business rules and attaching them to particular objects, you can ensure that a database performs the required tasks.
For further discussion of database design, see Designing Your Database.
Detailed information about SQL Modeler is contained in the SQL Modeler Users Guide, included in the on-line documentation.