MERGE VARIABLES enables you to merge the variables of one dataset with the variables of another dataset to create a third dataset that has both sets of variables in it.

The variables in the current dataset (the highlighted one) are merged with those in the previously current dataset (the one current before the current one). In the new dataset, the variables in the previously current dataset will appear before those in the current dataset.

The two datasets that are merged must have the same number of observations (rows). Usually, it does not make sense to merge variables unless the observations in the two datasets are the same, and in the same order, although ViSta does not check on this.
