Currently all of the generated update rules have a where clause (where field is null) There are several situations where this makes it very hard to use map and auto generated rules.
1. When there is a bit field and you default it to false(0). If you now want to fill the flag field to true using map, it will never update because the field is never null.
2. When there is a target override value. Example: All the source mapping is complete, then there is a target rule that says for all intercompany customers this field is supposed to be "01". Because the source mapping might have filled the value, you can't override it with a generated rule because of the (where field is null).
We can leave the where clause as the default but allow for each mapping to override that or a check box "only update if null" that is always checked but can be turned off on during mapping.
Looks to me like we need a flag (checkbox) on the Rule in MAP to allow the developer to choose to include the IS NULL where clause or not. This indicator would be defaulted to ON for all fields unless the field type is BIT where it should be defaulted to OFF.