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.

When column pairs are linked by a reference, each value in the child table column refers to an equivalent value in the parent table column.

Within a reference, each column pair is linked by a join. Depending on the number of columns in the primary key, or alternate key, or the number of specified columns, a reference can contain one or more joins.

A reference normally links primary key, or alternate key, columns to foreign key columns.

Example

The two tables SALE and STORE are linked by a reference. STORE is the parent table and SALE is the child table. The reference contains 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 to create default references between PK columns in one table and columns with identical code and data type in another table. Note that rebuilding is not possible between two tables with PK columns.
• Displaying Referential Integrity and Cardinality on Reference Symbols
  To set display preferences for references, select Tools > Display Preferences, and select the Reference sub-category in the left-hand Category pane.