MySQL group query gets the largest record of a field in a group

ID SID CID
1 1 1
2 1 2
3 2 1

To the SID group, the last to take the largest CID, the above to take 2nd, 3

1 method One:2 Select *  from(Select *  fromTableOrder  byCiddesc) asAGroup  byA.sid3 4 Method Two:5 SelectA.*  fromTable asAwhereCid=(Select Max(CID) fromTablewhereA.sid= SID)6 7 Method Three:8 SelectA.*  fromTable asAwhere  not exists(Select *  fromTablewhereSid=A.sid andCid>a.cid)9 Ten method Four: One SelectA.*  fromTable asAwhere exists(Select Count(*) fromTablewhereSid=A.sid andCid>A.cid having Count(*)=0)

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MySQL group query gets the largest record of a field in a group