It was astonished for me that databases like MS SQL and Sybase do not support ordering and union by columns of the TEXT type (and some other data types, in short big data blobs). It seems the reason is logical. I would suppose it is performance hit to compare such big data sets that could be stored in such columns. So when you change legacy data type to text be sure that somewhere else this column is not a part of such operations. Or you will caught unpleasant regression as I did.