| (: XQuery Aggregate Query :) | |
| (: Find the number of wind sensor readings. :) | |
| fn:count( | |
| let $collection := "ghcnd_quarter_1|ghcnd_quarter_2|ghcnd_quarter_3|ghcnd_quarter_4" | |
| for $r in collection($collection)/dataCollection/data | |
| where $r/dataType eq "AWND" | |
| return $r/value | |
| ) |