Desktop User Guides > Professional > Data management scripting > Merging case data > Running a vertical merge
Running a vertical merge
If there are no JoinKey parameters in the InputDataSource sections see Running a horizontal merge, a vertical merge takes place (see How a vertical merge works) when you run the data management (DMS) script.
The DMS script does not automatically renumber Respondent.Serial when writing cases to the output data. Therefore, all cases from all input data sources will retain their original values of Respondent.Serial, which might result in duplicate values. This might cause a problem when using output data sources, such as the Relational MR Database DSC, that do not allow duplicate serial numbers. In addition, once the merge is complete, it might be difficult to identify which cases originated from which data source.
To avoid these problems, do one of the following:
Create a new value for Respondent.Serial as each case is written to the output data. Typically, you would start with a value of one and increase the value by one for each case.
Allocate values for Respondent.Serial in unique ranges depending on the input data source. For example, the cases from your master data source might be allocated values from 1 to 1,000; the cases from your second input data source might be allocated values from 1,001 to 2,000; and so on.
Regardless of which approach you use, you might also want to add new variables to the output metadata, so that for each case you can store the original value of Respondent.Serial and other information about the input data source.
For more information about these approaches, see following sections.
Creating new values for Respondent.Serial
Allocating Respondent.Serial in ranges
Merging case data