Final answer:
To merge three datasets in SAS in one DATA step, they must have a common variable to use as a key. The merger uses the MERGE statement, optionally with BY statements for alignment. Proper alignment and handling of duplicates or mismatches are crucial during this process.
Step-by-step explanation:
The student has asked about merging three datasets in SAS using a DATA step. The possibility of merging these datasets depends on the nature of the variables in each dataset (such as having a common identifier) and the desired outcome of the merge. Without the specific structure of the tables, it's impossible to give a definitive answer. However, in general, merging datasets in SAS is done using the MERGE statement, sometimes along with BY statements if there is a key to merge on. If all datasets contain a common variable that can act as a key, they can likely be merged in one DATA step.
To actually merge the datasets, you would begin with a DATA statement to create a new dataset followed by a MERGE statement listing the datasets you want to merge. If the datasets are related by some common variables, you can then use a BY statement to specify the common columns. When merging datasets, it's crucial to ensure that the data is properly aligned and that any duplication or mismatches are addressed.