Chapter 6 Working with PDMs

Modifying the mapping of a column

You can modify the default mapping created for a column. The Column Mappings property sheet can be used to fine-tune the mapping between a column in the current table and columns in other tables in the data source.

In the "Mapped to" box, you can see the column expression. By default, columns used in this expression are prefixed by their tables. You can customize the content of the "Mapped to" box by inserting comments manually. You can also click the Ellipsis button and use the SQL Editor to modify the default mapping syntax. To recover the default column expression, click the User-defined tool.

In the Sources tab it is possible to select several columns and map them to the current column. To do so, you have to use the Add Sources tool to select columns from the list of columns belonging to the tables mapped to the current table. When you add columns from the Sources tab, and the column expression has not been modified by the user, the content of the "Mapped to" box in the General tab is updated.

For example, you define a mapping between table TOTAL_SALES in Model_1 and tables EUROPEAN_SALES in Model_2 and ASIAN_SALES in Model_3. Each table has a column called TOTAL AMOUNT. You can define column TOTAL AMOUNT in TOTAL_SALES as the sum of total amounts in EUROPEAN_SALES and ASIAN_SALES:

To modify the mapping of a column:

1. In the Mapping tab, select the Columns Mapping sub-tab to display the corresponding sub-tab.
2. Select a column in the list and click the Properties tool to display the Column Mappings Properties dialog box.
3. Click the Sources sub-tab and click the Add Sources tool to select source columns from a selection dialog box and click OK.
   
   The columns appear in the Sources list.
4. Click the General tab to display the corresponding tab. The selected columns appear in the "Mapped to" box.
5. Click OK.

Copyright (C) 2005. Sybase Inc. All rights reserved.