Hi, I encountered an issue when using the following code to get a combined data xy from data x and y:   data sdp; input name $ score1 score2 gender $ stu_id score4; datalines; Tim 88 80 m 1 98 Sharon 95 90 f 2 90 Sean 45 78 m 3 . Mike 89 . m 4 . Tina 54 69 f 5 60 Sara 67 78 f 6 80 Noah 89 78 m 12 85 ;;; data sda; input name $ score1 score2 score3 gender $ stu_id; datalines; Tim 88 80 99 m 1 Sharon 95 90 90 f 2 Sean 45 78 56 m 3 Mike 89 . 77 m 4 Tina 54 69 69 f 5 Sara 67 78 74 f 6 Sam 98 82 78 m 7 James . 96 89 m 8 Jaden 98 78 89 m 9 Jack 69 79 70 m 11 Will 92 89 98 m 10 ;;; data x (keep = stu_id name score4 ); set sdp; run; data y (index=(Sid_name=(stu_id name))); set sda; run; data xy; set x; set y key=Sid_name; run; In the final data after combing, xy, the last record (#7) which has no matching record in y initially has no values for score1- score3 and gender, but in the combined date xy it comes with values and the same values for columns score1- score3 and gender are the same as the record #6. What could be the reason? Thanks! ... View more