If this is a one-off you could do:
UPDATE issues
SET category = (SELECT MIN (k.category)
FROM keywords k
WHERE i.description LIKE '%' + k.keyword + '%')
FROM keywords k
I will be really slow.
If you need to do this on a regular basis, you need to consider full-text indexing.
[font="Times New Roman"]Erland Sommarskog, SQL Server MVP, www.sommarskog.se[/font]