Okay so I'm writing a query to remove a specific item from every character wheres what I have

mind you I have about 10 days experience with sql

Code:
UPDATE `Characters`
SET Items='-1%'
WHERE Items LIKE %'3840'%;

although this will change items field to -1 instead of something like

2826, 2606, -1, 2765, -1, -1, -1, 2766, -1, -1, -1, 2762