To update data source files, edit and
save the data source file in comma- or tab-delimited format, and
then choose Update Data Source from the Data Merge panel.
The changes will be reflected in the Data Merge panel.
If the changes are not reflected in the document after updating,
deselect Preview to turn it off, and then select Preview again to
turn it back on.
To remove the connection to the data source file, choose
Remove Data Source from the Data Merge panel menu.
To switch to a new data source file, choose Select Data
Source from the Data Merge panel menu, and then specify the new
data source file. InDesign may not recognize some of the fields.
In this situation, it’s best to delete and reinsert placeholder
fields.
If you generate a merged document from
a target document in which data fields appeared on master pages,
you can update the data fields in the merged document.