Link Definition (Magic xpa 3.x)
Magic xpa's Link definition establishes one-to-one relationships between related database tables. The current record of the task's main file is correlated or linked to a specific single record of another database table whose key segments contain values that match the Link criteria. Links can be established to:
Perform validity checks
Verify that a particular record exists in the linked file
Extend the record data view by selecting variables from linked files
View, modify, or create records in the linked file
You define Link operations in the Data View Editor, where the task data view is established.
Link operations are part of the instructions to Magic xpa for creating the data view's logical record. Thus Magic xpa establishes initial links during the record data view preparation. When the link is established, you can use Link definitions to add variables of the linked file to the record data view. Linked variables are treated exactly the same as the variables selected from the main data object.
An important characteristic of the link is that it is dynamic. If the Link definition's expression values change during the main data object record processing, the link is automatically re-established and new linked record variable values are set.
When you create a Link operation, the Index Segments are automatically defined as columns within the Link section.
Wildcards are not applicable when used in a Link operation.
To implement one-to-one relationships between the Main Source and other database tables
To search for individual records in a data object
To validate information against data from another data object
Recomputing Link Expressions