If a crystal report has been built using a different database to the one you want to preview it with in Crystal, for example against a test/play database, the connections can be updated so that it looks at the correct tables.

Open the crystal report you wish to update, and click on Database=>Set Datasource Location

A window will open showing your current data source in the top section, and available data sources in the bottom section:

Select the database you wish to update to in the bottom section; if you are not already connected, you will be asked for your password:

Once connected, select the first table in the top section that you wish to replace, select the corresponding table in the bottom section and then click ‘Update’:

There will now be tables listed against two data sources in the top section:

Repeat for all tables under the old data source in the top section, until they are all listed under the correct database, then ‘Close’. When you preview your report, it will now pull data from the updated data source.