Try replacing MIN(xx.x); with MIN(xx::x);

The xx.x syntax returns a scalar IF the xx relationship only has one tuple.
If it doesn't it fails. The xx::x syntax refers to the x values in the xx

This is a common cause of confusion that we're looking to correct.

On Wed, Jun 20, 2012 at 8:15 PM, Yang <[EMAIL PROTECTED]> wrote:

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