Data Modeling: acknowledging the basic concepts


The basic concepts

Table : a relational table.

Column : an attribute of the table.

Association : a graphical representation of a relationship between at most two tables.

Role : each side of the association. Qualifies each table's implication in this relationship.
Role multiplicity : the number of occurrences of the related table.
Role navigability : indicates if this table is a child or a parent table.
Role constraint type : referential integrity implementation mechanism.

Key: primary , unique or foreign .
Key dependency: for primary and unique keys.
Referenced constraint: source of the foreign key constraint. May be a primary or unique key.




Building a data model

A relational data model consists of tables with non-decomposable columns and binary associations. A data model is used as a communication vehicle to build and describe databases.

It is possible to create a data model from the main menu, from the explorer window and from the edit toolbar.

By default, a data model comes with a diagram. Here is how to display it:
  1. Click the handle next to the data model in the explorer window, Diagram will appear.
  2. Right-click Diagram.
  3. From the pop-up menu, choose Show diagram.

The diagram appears on the right side of the explorer window. If it is empty, right-click inside the diagram window and from the pop-up menu choose Add Missing Graphical Representations.

If you do not want the data model to be automatically created with a diagram, change the default settings. See Modifying the options.

To add a target system, see Target system.