KPI shows the error- 'java.lang.Exception: Query Execution Failed ! :A column has been specified more than once in the order by list. Columns in the order by list must be unique'. Why?

KPI shows the error- 'java.lang.Exception: Query Execution Failed ! :A column has been specified more than once in the order by list. Columns in the order by list must be unique'. Why?

Possible reasons for this exception is: 1. KPI fails to execute a Crosstab KPI, if the 'ORDER BY' clause contains two columns. The columns specified must be unique 2. Ensure that the measure 'ORDER BY' defined is 'None'