Building Physical Diagrams

A physical data diagram provides a graphical view of your database structure, and helps you analyze its tables (including their columns, indexes, and triggers), views, and procedures, and the references between them.

You build a physical diagram at the end of the data analysis process, before you start the software programming. The physical diagram allows you to define how data from conceptual model are implemented in the database.

• Physical Diagram Objects
  PowerDesigner supports all the objects necessary to build physical diagrams.
• Creating a Physical Diagram
  You can create a physical diagram in an existing PDM in any of the following ways:
• Tables (PDM)
  A table represents a collection of data arranged in columns and rows. Tables may contain any of the following objects:
• Columns (PDM)
  A column contains an individual data item within a row. It is the model equivalent of a database column. A column is always defined for a table. When you create a column, it must be assigned a name and code. You can also select a data type for the column. This can be done directly from a list of available data types, or by attaching the column to a domain.
• Keys (PDM)
  A key is a column, or a combination of columns, that uniquely identifies a row in a table. Each key can generate a unique index or a unique constraint in a target database.
• Indexes (PDM)
  An index is a data structure associated with a table that is logically ordered by the values of a key. It improves database performance and access speed.
• Defaults (PDM)
  A default is a value that can be assigned to a column or a domain in the DBMS of the Sybase Adaptive Server Enterprise and Microsoft SQL Server families.
• Domains (CDM/LDM/PDM)
  Domains help you identify the types of information in your model. They define the set of values for which a column/entity attribute is valid. Applying domains to columns/entity attributes makes it easier to standardize data characteristics for columns/entity attributes in different tables/entities.
• Sequences (PDM)
  If your DBMS supports sequences, then you can create a sequence for a column.
• Abstract Data Types (PDM)
  An abstract data type (ADT) is a user-defined data type which can encapsulate a range of data values and functions. The functions can be both defined on, and operate on the set of values.
• References (PDM)
  A reference is a link between a parent table and a child table. It defines a referential integrity constraint between column pairs for a primary key, or alternate key, and a foreign key, or between user specified columns in both tables.
• Views (PDM)
  A view is an alternative way of looking at the data in one or more tables. It is made up of a subset of columns from one or more tables.
• View References (PDM)
  A view reference is a link between a parent table or view and a child table or view. It is used to define a set of predefined joins between the columns of the parent and the child table or view.
• Check Parameters (CDM/LDM/PDM)
  Check parameters are set of conditions which data must satisfy to remain valid.
• Business Rules (CDM/LDM/PDM)
  A business rule is a rule that your business follows. This can be a government-imposed law, a customer requirement, or an internal guideline.