Chapter 3 Building Physical Diagrams
Column details indicate common data constraints. The following table lists column detail parameters:
| Parameter | Description |
|---|---|
| Null Values | Percentage of column entries for which a null value is permitted |
| Distinct Values | Percentage of column entries for which a distinct value is permitted |
| Average Length | Average length of a value |
| Test Data Parameters | Test data profile selected from the dropdown listbox. Profiles can use characters, numbers or date/time data types |
| Computed Expression | Computed expression typed directly in the Computed Expression pane or defined with the SQL Editor (accessed with the Edit tool) which helps you define more complex expressions |
The percentage you type in this box defines the percentage of distinct values allowed in a column of a given table. This property is used during test data generation.
For example, you generate a table with 2 columns and 10 rows. You set the percentage of distinct values to 100 % for Column 1 and to 80% for Column 2. This implies that 10 rows must have distinct values in Column 1, and 8 rows in Column 2.
When you apply a test data profile with a list generation source to a column with a given percentage of distinct values, PowerDesigner uses the values from the test data profile list. If there are not enough values declared in the list, a warning message appears in the Output window to inform you that the distinct value parameter cannot be enforced due to lack of distinct values in the list of values.
For more information on test data parameters, see the "Using test data" section in the Generating a Database from a PDM chapter.
For more information on defining computed columns, see "Creating a computed column".
| Copyright (C) 2005. Sybase Inc. All rights reserved. |
| |