What does the SET statement accomplish in a DATA step?

The SET statement in a DATA step is primarily used to read data from an existing dataset. This functionality allows you to access and manipulate the data stored in that dataset for further processing in your SAS program. When the SET statement is invoked, SAS will retrieve the observations and variables from the specified dataset, which can then be used in the DATA step to create new variables, modify existing ones, or perform calculations.

By taking data from an existing dataset, the SET statement enables users to harness previously stored data for analysis or transformation. It is a foundational element in data manipulation within SAS, facilitating various tasks such as filtering, sorting, or merging datasets once they are in the DATA step for processing.

In contrast, reading data from an external file typically involves the use of other statements, such as the INFILE statement combined with the INPUT statement, rather than the SET statement. Similarly, while combining datasets can be accomplished, it generally requires the use of the MERGE statement or a SQL procedure rather than solely relying on the SET statement. Generating summary reports also falls outside the primary function of the SET statement and is typically handled through procedures like PROC REPORT or PROC PRINT.