UPDATE m_product
SET em_mg_longdescription = regexp_replace(em_mg_longdescription,'------------',chr(13))
WHERE
em_mg_manufacturer = 1000637
AND value = 'IMI-YW356A01'
Some additional replace scripts
UPDATE m_product
SET em_mg_longdescription = regexp_replace(em_mg_longdescription,'</li>',chr(10))
WHERE
em_mg_manufacturer = 1000637
UPDATE m_product
SET em_mg_longdescription = replace(em_mg_longdescription,'<li>','')
WHERE
em_mg_manufacturer = 1000637
UPDATE m_product
SET em_mg_longdescription = replace(em_mg_longdescription,'<ul>','')
WHERE
em_mg_manufacturer = 1000637
UPDATE m_product
SET em_mg_longdescription = replace(em_mg_longdescription,'</ul>','')
WHERE
em_mg_manufacturer = 1000637