Env:
ruby 2.2.3
mysql2 0.4.3

CLIENT = Mysql2::Client.new(host: '<host>', username: '<uname>', password: '<pwd>', database: '<db>', read_timeout: 10)

update_str = %Q(UPDATE marcom
SET `value` = "<subject>"
WHERE campaign_id = ?
AND flow_key = "<xyz>")

stmt = CLIENT.prepare(update_str)

result = stmt.execute(campaign_id) #campaign_id coming from somewhere else
# result is nil