Yes, DESelect provides the ability to use SQL functions to provide full flexibility on the transformations you perform on your fields.
This is possible through the Apply Formula To a Field of the Custom Values feature.
To use SQL functions:
> Navigate on the Target Definition screen.
> Create a new custom value by clicking the Add New Value button.
> Choose Apply Formula to a Field followed by Apply Any Function.
More details on how this functionality works can be found below: