The external parameter has not had a value assigned to it.
Response
Provide a value for the parameter when calling op:result, xdmp:sparql etc. If you are not using these functions, then MarkLogic has no method to provide values for external parameters - you should assign the parameters a value directly in the query.
Stack Overflow: Get the most useful answers to questions from the MarkLogic community, or ask your own question.
Stack Overflow: Get the most useful answers to questions from the MarkLogic community, or ask your own question.