dataassist has made your select statement like this...
SELECT * FROM Testimonials ORDER BY tID DESC
replace the * with the field names you need with a comma between them
for example to add only tID and tTEXT
SELECT tID, tTEXT FROM Testimonials ORDER BY tID DESC
to modify tTEXT to only 150 characters you need
SELECT tID, left(tTEXT,150) as tTEXT150 FROM Testimonials ORDER BY tID DESC
ALTERNATIVELY...
skip the sql modification and do it all with a couple more lines of php, setting the $cutoff to the length you need
<?php
$cutoff = 150;
$extract = $row_WADATestimonials['tTEXT'];
$extract = substr($extract, 0, $cutoff);
$lastspace = strrpos($extract, ' ');
$extract_word = substr($extract, 0, $lastspace).'...';
echo nl2br($extract_word);
?>