In the situations where a target table exists, column mapping must not alter the physical target table. New target columns cannot be added, but adjustments can be made to alter the source feed. The screen appears slightly different, as their is a new Populate Columns Panel.
The Column Mapping to Existing Target Table screen appears as:
Let suppose that ProductQuantity was no longer desired. The user must navigate to the ProductQuantity column on the Source Column, and blank it out. This will prevent ProductQuantity from being used. Derived Fields can be changed, but the Target Table Column that the Derived Column feeds to CANNOT be altered.
For cases where the Designer wishes to have the flexibility of mapping each column individually, the "CLEAR TARGET/CLEAR SOURCE buttons were created. This has the net effect of clearing either the Source Mappings or Target Mappings. This is generally done in the case where there is a large discrepancie between the Source Feed, and the existing Target Table.
Example 1:
Target Table A had 1000 columns, but the source feed only represented 10 Columns.
The designer might do the following:
1. Select Source Columns radio button, and press the Clear Target. This will remove the Target Mappings from the screen.
2. Individually map each Target Column to the Source Column. This is accomplished by using the Drop-Down List box for the Target Column names. You will need to do this for the 10 columns desired.
Example 2:
Target Table A has 10 Columns, but the Source Feed has 10000 columns.
1. Select Target Columns radio column, and press the Clear Source. This will remove the Source mappings from the screen.
2. Individually map each Source Columns by using the Drop-Down list box for the Solumn Column Names. You will need to do this for the 10 columns desired.
In certain scenarios, the Designer might want to Clear the Source or
Target Columns. This might be done in the case where the Target Table
has hundreds of columns, and the designer wants to map a source feed that
is much smaller.