Using max function with dates in xquery

[DaronRyan]

I am trying to find the maximum date in an xml file using xquery. I believe I shold be able to do so using the following.

Code: Select all

declare namespace q2 =  "http://daron.ryan.org/namespace/q2.html";

<younger_workers>

{

    let $workers:= doc("q2.xml")//q2:workers

    let $youngest :=xs:date(max($workers//q2:bdate))

    return  $youngest

}

</younger_workers>

however this error message occurs:

SystemID: null
Description: E Failure converting {1975-02-20} to a number

This code

Code: Select all

declare namespace q2 =  "http://daron.ryan.org/namespace/q2.html";

<younger_workers>

{

    let $workers:= doc("q2.xml")//q2:workers

    let $youngest :=xs:date(max($workers//q2:bdate))

    let $copy := $youngest 

    return  <blank></blank>

}

</younger_workers>

produces the same message. Deleting the line

Code: Select all

 let $copy := $youngest

gets rid of the error. I cannot use

Code: Select all

$youngest

variable in any way without causing the error. Can anyone explain what is wrong?

Regards,
Daron.

[alex_jitianu]

Hello,

All items in the argument of the max() function must be numeric or derived from a single base type.
So the items from "$workers//q2:bdate" are being converted to numeric type but something like {1975-02-20} cannot be converted to a number.

You can try the following code :

Code: Select all

declare namespace q2 =  "http://daron.ryan.org/namespace/q2.html";

<younger_workers>

{

    let $workers:= doc("q2.xml")//q2:workers

    let $dates :=$workers//q2:bdate

    let $youngest :=max(for $date in $dates  return xs:date($date))

    return  $youngest

}

</younger_workers>

Hope it helps,
Alex

[DaronRyan]

Hello Alex,

I quickly tried you suggestion and it worked.

Thank you,
Daron.