Merging Data - Snap Surveys

This worksheet explains how to use the Database Link Wizard to import data from another Snap survey even where the two surveys are not identical.
For details of importing/exporting data to a database package click here.

Importing/exporting data to another Snap survey

Snap can import and export data, variables and codes between Snap surveys even if the variables and codes are not identical.
The easiest way to do this is using a database link to import or export the data.
This method can be used to merge surveys:

Archive the survey you want to add data to, in case of accidents.
Open the survey that you want to add data to.
Click on the Snap toolbar to open the Database Linkage dialog.
Click [New…] to create a new database link. The Database Linkage Wizard dialog will be displayed.
Select Import from Survey.
Click [Next>].
Select a survey to import from. Snap lists all the surveys available in the default directory. If the survey you require is not in this directory use the [Browse…] button to find the appropriate directory.
Click [Next>] when you have highlighted the survey you require.
Snap displays another dialog.
Select the type of Import/Export Options to use.
Join cases where the link variables match:
Only import/export data where the value in the link variable matches between the two surveys (E.g. a survey containing customer ID numbers matches the information in the link survey with the same ID number.) Snap imports all requested data where two ID numbers are matched, and ignores all data in cases where the ID number does not match.
Join matching cases and append unmatched cases:
This option works as above, and also adds the unmatched data as new cases at the end of the file.
Append unmatched cases:
This option only imports/exports cases that do not find a match between the link variable in the surveys.
Append all cases:This option imports/exports every case of data into your survey as a new data case. It does not try to match the link variables.

If you select Append all Cases you do not need to define a link variable.
If you select any of the other import types, select the link variable in your current survey.
Select the variable containing the matching data in the survey you are importing from.
The link variables must contain a value that is unique for each case, and which match between the two surveys. For example they could both be ‘Customer ID’ variables. (Link variables are also known as database keys).
Click [Next] to move to a dialog showing a list of variables in survey to import from on the left, with variables in the current survey on the right.
Map the variables between the surveys. Snap works out the mapping between the variables where possible. To change a mapping, select a row in the right hand column, and click to display a list of available variables in the import survey. Select a variable to load data from, or select a blank to load nothing.

If you match variables with multiple responses, Snap displays the possible responses below the variable list. Match the responses in the same way as you match the variables.
The example shows an extra code, wine/beer, is an extra code in the survey that you are importing data from. You can assign wine/beer to the Other code.

You could also create a new code in the current survey for wine/beer by right clicking the row and selecting New code from the context menu.
You can create a new variable to match an existing variable in the same way. Right-click in the right hand row, and select New variable from the context menu. If you created a variable, you can modify and delete it.
Click [Next] to display a summary of what the link does.
Check the details are correct, and enter a Name for the database link.
Click [Finish]. Snap shows the Database Linkage dialog including the new link.

If you wish to alter any part of the link, click [Modify]. To delete a link, click [Delete]. To make a copy of the link, click [Clone], and then modify the new link as required.
Select the link and click [Run] to import the data. Snap displays a brief report. Click [OK] to close it.
Check your data. This can be done by looking at a summary of the results.
Choose [View] and select [Questionnaire] click and choose [Counts] on the toolbar. Scroll down through the questionnaire checking the figures for each question are correct.