References (PDM)

A reference is a link between a parent table and a child table, which defines a referential integrity constraint between column pairs for a primary or alternate key and a foreign key, or between user-specified columns. Each column pair is linked by a join, and each reference can contain one or more joins. Each value in the child table column is equal to the value in the parent table column.

In the following example, the STORE parent table is linked to the SALE child table by a reference containing a join which links the primary key column STORE ID (the referenced column) to the foreign key column STORE ID (the referencing column).

• Creating a Reference
  You can create a reference that links a primary key, or alternate key, to a foreign key, or user-specified columns in both parent and child tables.
• Reference Properties
  To view or edit a reference's properties, double-click its diagram symbol or Browser or list entry. The property sheet tabs and fields listed here are those available by default, before any customization of the interface by you or an administrator.
• Automatic Reuse and Migration of Columns
  When you create a reference, PowerDesigner can automatically reuse an appropriate existing column in the child table as the foreign key column and migrate the primary key column in the parent table to create a foreign key column in the child table.
• Rebuilding References
  You can rebuild references at any time to create default references between PK columns in one table and columns with identical code and data type in another table. Rebuilding is not possible between two tables with PK columns. Rebuilding references can be useful following the reverse engineering of a database in which not all the references could be reverse engineered.
• Displaying Information on Reference Symbols
  You can display the cardinality, referential integrity, join, table roles and other properties on the source and destination ends and in the center of a reference. To set display preferences for references, select Tools > Display Preferences, and select the Reference sub-category in the left-hand Category pane.