How to use sub query in CI Active record classes?

[eluser]Rey Philip Regis[/eluser]
Hi guys,

Does anybody know how to use subquery in CI Active Record class? The query is like this

Code:

SELECT
cse.TRIAGECASEID,
(SELECT cmp.DESCRIPTION FROM `complaint` cmp WHERE cmp.TRIAGECASEID = cse.TRIAGECASEID AND cmp.ISCHIEFCOMPLAINT = '1') as `CHIEF COMPLAINT`,
cal.DATEANDTIME,
cse.SCORE,
tcasestatus.CASESTATUSTYPECODE
FROM
`case` cse
INNER JOIN
triagecasecall` tcasecal ON(cse.TRIAGECASEID = tcasecal.TRIAGECASEID)
INNER JOIN
`call` cal ON(tcasecal.CALLLID = cal.CALLLID)
INNER JOIN
`triagecasestatus` tcasestatus ON(cse.TRIAGECASEID = tcasestatus.TRIAGECASEID)
WHERE
cse.PATIENTID = '114'

Thanks in advance.