Thank you, Ksharp. First, I find that the temp file creates 17 duplicate observation. I am not sure what cause it. sort data=temp out=temp1 nodupkey; target _a_name _b_name _a_value _b_value; run; Second, if there is only 1 list of condition (a b c d e f) instead of a1-a3 and b1-b3, and I want to do the combination of this list with the following code, there are still a lot of duplicate observation. definitely, the problem is kind of AB and then BA. I don't know how to eliminate this. I wonder if you could help me. Thank you, HHC data temp1(keep=_a_: _b_: target); set have; array _a{*} a b c; do i=1 to dim(_a); do j=i+1 to dim(_a); if _a{i}^=_b{j} then do; _a_name=vname(_a{i}); _b_name=vname(_b{j}); _a_value=_a{i}; _b_value=_b{j}; output; end; end; end; run;
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