You make the value shorter by using a built-in function such as LEFT() or SUBSTR(). For example, this:<pre>
Select itdsc FROM amflib7/itemasa</pre>
Select LEFT(itdsc,15) FROM amflib7/itemasa</pre>
And as Carlosdl says, EXISTS only tells you if any row meets your criteria. It <i>does not tell you</i> how many rows meet your criteria. You can only UPDATE your spdesc column with a single value. If there are multiple rows that satisfy your WHERE clause, the UPDATE will choke. You will then need to refine your WHERE clause to ensure a one-to-one match.
But that comes after this part works, and it might not be a problem anyway.