using a flag variable t default 0 if t=1 and date is not missing then output and set t=0(default) else if have single record then output else if first record and date have non missing value then output other wise set t=1 those records would be in output which are first nonmissing value of date there are two case 1. A single record then output same 2. if more same dup record nonmissing of date then output otherwise goto next record goto next record repeated until not found .
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