Hi My XML is as follows :

<root>
<course>
<reg_num>10499</reg_num>
<subj>GER</subj>
<crse>391</crse>
<sect>F</sect>
<title>German Thought Postmodrn Era</title>
<units>1.0</units>
<instructor>Irmscher</instructor>
<days>T-Th</days>
<time>
<start_time>02:40PM</start_time>
<end_time>04:00</end_time>
</time>
<place>
<building>ELIOT</building>
<room>414</room>
</place>
</course>
<course>
.....................
</course>
</root>

I need to display

<CourseInstructor instrName="Brightman">
<course>GER</course>
<building>ELIOT</building>
</CourseInstructor>
<CourseInstructor instrName="Makley">
<course>..</course>
<building>..</building>
</CourseInstructor>
<CourseInstructor instrName="Kaplan">
<course>BIOL</course>
<building>..</building>
</CourseInstructor>

My XQuery is

for $eachInstr in distinct-values(//instructor)
return element CourseInstructor
{
attribute {"instrName"} {$eachInstr},
for $courseName in distinct-values(//course[instructor = $eachInstr]/subj)
let $bldg := //course[instructor = $eachInstr and subj = $courseName]/place/building
return <course> {$courseName} </course> , <building> {$bldg} </building>
}

I get the error variable $bldg is not declared error

If I remove the building part I get proper output with just the course part.