to show the first 150 charcters only in a string, you can edit the sql as follows (for example)...
left(fieldname,150) as fieldname150.
to prevent half-words, you can look for the last space in the 150 character string and trim it again.
this can be done with a bit of php...
in the code recordset is the name of your mysql recordset
$extract = $row_recordset['fieldname150'];
$lastspace = strrpos($extract, ' ');
$extract_word = substr($extract, 0, $lastspace).'...';
you now have a new string variable called $extract_word with slightly fewer than 150 characters, but ending on a whole word, with an ellipsis tagged onto the end.
Here it is on a site news.php