1. Click File|Open Examples|Datasets to open "Cat Clinic Patient Info.sta" 

2. Click "Add to Workspace" under Home tab to insert the data into a workspace

3. Repeat Step 1 & 2 to insert "Cat Clinic Measurements (2000).sta" into the same workspace

4.  Under Data|Merge, select "Merge Variables" to insert the node.

5. Connect the two input datasets with the "Merge Variables" node and click the wheel icon on top left of the "Merge Variables"(circled in red) node to configure options.

6. Under the "Merge Variables" configuration dialog, click "Match variables" under Input to select matching variables for each merge data file. In this example, "Patient ID" from the first data and "ID" from the second data are selected respectively as they both represent cat ID. Note: The matching variables are not required to have same names but need to be in the same order regarding how they are listed.

7. Click "File 1 variables" and "File 2 variables" under Output select the variables to merge from the two data files.

8. Select an option under "Match Criteria by:" to specify how matching variables are compared

9. Under "File 1& File 2 Unmatched cases": Select an option to specify the manner of dealing with unmatched cases when the two files are merged. 

10. Under "Multiple cases", select an option to specify what to do if duplicate matching cases are encountered.

11. Under "Drop multiples",  use the options in this group box to specify how duplicate cases in the file should be handled.

12. Under "Input order", use this group box to specify the order of the output.

Note: Click "?" on top right of the Merge Variables dialog to learn details about each option of this session in the e-manual.