limit number of returned characters

[silx]

i am using this to display the result now::

<?=$w_data[$i]['Summary']?></td>

table SUMMARY
contains say 200+ characters in a field

how can i return a result but limit it by the first 20 or so

[Roger_Ramjet]

select left(col1 , 20) from summary

[bastien]

<?php echo substr($w_data[$i]['Summary'],0,20); ?></td>