So, I'm familiar with merges in SAS, and haven't had issues before, but I noticed an issue today that has never been an issue before. For some reason the actual merging of observations is working properly in more complex data sets, however it only lists the variable values from one of the data sets (e.g. it doesn't overwrite missing values). For instance, I wrote up this simple program:     data dataset1;     input id var1 var2 var3 var4;     cards;     1 . . 2 2     2 . . 2 2     3 . . 2 2     4 . . 2 2     5 . . 2 2     6 . . 2 2     7 . . 2 2     8 . . 2 2     9 . 2 . 2     10 1 . . .     ;     data dataset2;     input id var1 var2 var3 var4;     cards;     1  2 2 . .     2  2 2 . .     3  2 2 . .     4  2 2 . .     5  2 2 . .     6  2 2 . .     7  2 2 . .     8  2 2 . .     10 . 1 . .     ;               data dataset3;     merge dataset1 dataset2;     by id;     run; This should yield the following:     id var1 var2 var3 var4     1   2    2    2    2     2   2    2    2    2     3   2    2    2    2     4   2    2    2    2     5   2    2    2    2     6   2    2    2    2     7   2    2    2    2     8   2    2    2    2     9   .    2    .    2     10  1    1    .    .     but instead, I get this:       id var1 var2 var3 var4         1   2    2    .    .         2   2    2    .    .         3   2    2    .    .         4   2    2    .    .         5   2    2    .    .         6   2    2    .    .         7   2    2    .    .         8   2    2    .    .         9   .    2    .    2         10  .    1    .    . So, it's as if the merge is merging the observations and then just displaying the second data set's values. I've tried to figure out the issue (I have a feeling it's something very basic I've just looked over), but I've no idea what's happening, since I've never come across the issue before. Anyone know what's going wrong? Thanks for any help. ... View more