db={"health":[{healths:{"healthCd":"D","healthName":"ABC","effDate":"2012-08-24T07:16:33"}},{healths:{"healthCd":"C","healthName":"MONO","effDate":"2012-08-24T07:16:33"}},{healths:{"healthCd":"E","healthName":"BONO","effDate":"2012-08-24T07:16:33"}},{healths:{"healthCd":"B","healthName":"JOJO","effDate":"2012-08-24T07:16:33"}},{healths:{"healthCd":"A","healthName":"KOKO","effDate":"2012-08-24T07:16:33"}},{healths:{"healthCd":"1","healthName":"LULU","effDate":"2012-08-24T07:16:33"}},{healths:{"healthCd":"E","healthName":"BOBO","effDate":"2014-07-26T22:37:49"}}]}

db.health.aggregate([{$sort:{"healths.effDate":1}},{$group:{_id:"$healths.healthCd",healths:{$first:"$healths"}}},{$replaceRoot:{newRoot:"$healths"}}])