Please refer to various event correlation techniques that Splunk offers: http://docs.splunk.com/Documentation/Splunk/6.5.0/Search/Abouteventcorrelation
I feel stats command with by parameter as your unique identifier should suffice the need. You might have to provide search and data example for further assistance.
Refer to another one of my answers on how Stats can be used to correlate events.
Send some sample data/field names and I would be able to assist.
Stats can perform event correlation which you need kindly give some data sample and I can help. Were you able to go though documentation on how stats can perform correlation?
Looks like you need to setup event parsing configuration (props.conf on Indexer/Heavy Forwarder) to use proper line-breaking to merge related lines (based on log data format) into one event. See this for more information on the line breaking part of event processing. http://docs.splunk.com/Documentation/Splunk/6.5.0/Data/Configureeventlinebreaking
For better suggestions, please share your sanitized sample data.
There is no easy way to do this but happily, it would not be worth the effort to do it even if there was. It makes the most sense to (as much as possible) keep the raw events in their native format. Assuming that the "unique identifier" that you describe is called
mid, you can easily do things like this in search to aggregate the raw events into a conglomerated event:
... | stats (*) AS * BY mid
... | stats range(_time) AS duration list(_raw) AS events BY mid