Research Design and Statistical Consulting
George M. Diekhoff, Ph.D.

Merging Data Files

One of my clients had to send me data in waves as it became available. The cases in each incoming wave were about the same, with a few new cases added and a few old cases missing, but each incoming data file included some new variables. 

How does one merge SPSS data files like this? As long as all cases in all files have unique identifying code number, it’s simple. Let’s call the variable that contains identifying code numbers CaseID. 

Let’s call the data file you are adding on to Data1 and the new file to be merged into Data1 will be called Data2.
1. Sort cases in both data files by CaseID as follows: Data > Sort Cases > move CaseID to “Sort by” window. Choose “Ascending” Sort Order > OK.
2. Save each file after sorting the cases by CaseID in ascending order.
3. Keep both files open, but activate Data1, i.e., have it showing on your screen.
4. Data > Merge Files > Add Variables > highlight Data2 > Continue.
5. Highlight CaseID in the “Excluded Variables” window > check “Match case on key variables” > move Case ID to “Key Variables” window by clicking on the arrow > OK.