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BY-group merge
Learn BY-group merge in SAS through the exact construct, a dedicated example, a boundary case, and a mastery check.
BY-group merge is an atomic SAS lesson inside Merging & Reshaping. The example uses the specific syntax, command, API, instruction, or language rule named by this lesson.
Study the construct itself, then change one relevant input and predict the result before running it. That keeps this lesson focused on BY-group merge rather than on generic SAS syntax.
Topic-specific example
proc sort data=work.a; by id; run; proc sort data=work.b; by id; run; data work.m; merge work.a work.b; by id; run;
For BY-group merge, inspect the SAS log as well as the output data set; type conversion, missing values, and BY-group ordering can change results without stopping execution.