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"Unknown Query Engine" Error Running a Crystal Report

Updated 02/17/2011 - Article ID#: KWin0025


"Unknown Query Engine" is a very generic error generated by Crystal Reports. The error message does not provide any specific reasons for the error, but there are few possible solutions listed below.

6/22/2006 - In RDPWin Revision 1.236, the size of the Units.DAT file changed from 256 bytes per unit to 512.   Any Crystal report that uses the Units.DAT file displays an "Unknown Query Engine" error until that report is changed with the procedure below:


Run Crystal Maintenance on the report.

  1. In RDPWin, go to the System main menu --> File Utilities --> Crystal Maintenance.
  2. Select the report folder for which the specific report resides, i.e. FrontDesk or Res folder. Do not run Crystal Maintenance on the entire Reports10 folder.
  3. Click the Change button.

Verify Database in Crystal Reports Designer version 11 or 2008.

  1. Open Crystal Reports.
  2. Open the report displaying the error message.
  3. Click Database --> Verify Database.
  4. Crystal will detect any problems with file linking, file names, formulas, etc. Once prompted with "The database is now up to date," click OK.
  5. Save the report and try running it again in RDPWin.
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