TEXT in select

Hi,

does anybody know a way, how to implement the content of a field of type
TEXT
into a query?

if i am trying:
select * from testtable WHERE testTEXT LIKE '%testString%'

i am getting always an empty selection, although there is a record existing.
The same with

select * from testtable WHERE position ('testString' in testTEXT) >
0;

Additional, is there a way to use the UPPER()-function to the content of the
TEXT-field?

Thanks in advance,
Michael