Feature request: ability to UNION CDbCriteria objects.
I tried creating a class UnionCriteria which extends CDbCriteria and contains several CDbCriteria objects. I needed to use UnionCriteria with CActiveDataProvider on page with paging and filtering so redefining createFindCommand() and createCountCommand() of CDbCommandBuilder was enough. Had a problem with replacing CDbCommandBuilder with descendant.
My solution works, though I had to edit yii code (when replacing CDbCommandBuilder).