How to write an xquery containing sequence elements? - sql-server

Question

I've got a very large xml data set that is structured like the following:
<root>
<person>
<personid>HH3269732</personid>
<firstname>John</firstname>
<lastname>Smith</lastname>
<entertime>01/02/2008 10:15</entertime>
<leavetime>01/02/2008 11:45</leavetime>
<entertime>03/01/2008 08:00</entertime>
<leavetime>03/01/2008 10:00</leavetime>
...
// number of enter times and leave times vary from person to person
// there may not be a final leave time (ie, they haven't left yet)
</person>
...
</root>
The structure of the data is not under my control. This data is currently residing in a single xml column in a single row in MS SQL Server 2005. I am trying to construct a query which results in the following output:
HH3269732 John Smith 01/02/2008 10:15 01/02/2008 11:45
HH3269732 John Smith 03/01/2008 08:00 01/02/2008 10:00
HH3269735 Mark Pines 02/01/2008 09:00 NULL
HH3263562 James Frank NULL NULL
HH3264237 Harold White 04/18/2008 03:00 04/18/2008 05:00
...
My query currently looks like the following:
DECLARE #xml xml
SELECT #xml = XmlCol FROM Data
SELECT
[PersonId] = Persons.PersonCollection.value('(personid)[1]', 'NVARCHAR(50)')
,[First Name] = Persons.PersonCollection.value('(firstname)[1]', 'NVARCHAR(50)')
,[Last Name] = Persons.PersonCollection.value('(lastname)[1]', 'NVARCHAR(50)')
??????
FROM #xml.nodes('root\person') Persons(PersonCollection)
That query may not be 100% right as I'm pulling it from memory, but the problem I'm having is that I don't know how to include the entertime leavetime sequence elements in such a way as to get the desired rowset that I indicated above.
Thanks.
UPDATE:
I wanted to add that a given person record may have no entertime/leavetime sequence elements at all, but still needs to be returned in the rowset. I have updated the example of the desired output to reflect this.

Answer 1

with cte_entertime as (
SELECT
[PersonId] = t.c.value('(../personid)[1]', 'NVARCHAR(50)')
,[First Name] = t.c.value('(../firstname)[1]', 'NVARCHAR(50)')
,[Last Name] = t.c.value('(../lastname)[1]', 'NVARCHAR(50)')
,[Entertime] = t.c.value('.', 'NVARCHAR(50)')
,[entry_number] = ROW_NUMBER() OVER (ORDER BY t.c)
FROM #x.nodes('root/person/entertime') t(c))
, cte_leavetime as (
SELECT
[Leavetime] = t.c.value('.', 'NVARCHAR(50)')
,[entry_number] = ROW_NUMBER() OVER (ORDER BY t.c)
FROM #x.nodes('root/person/leavetime') t(c))
SELECT PersonID
, [First Name]
, [Last Name]
, [Entertime]
, [Leavetime]
FROM cte_entertime e
LEFT OUTER JOIN cte_leavetime l on e.entry_number = l.entry_number

Answer 2

I have accepted Remus's answer as it got me 95% to the solution. For informational purposes, here is the final query structure:
with cte_maindata as (
SELECT
[PersonId] = t.c.value('(personid)[1]', 'NVARCHAR(50)')
,[First Name] = t.c.value('(firstname)[1]', 'NVARCHAR(50)')
,[Last Name] = t.c.value('(lastname)[1]', 'NVARCHAR(50)')
FROM #x.nodes('root/person') t(c))
, cte_entertime as (
SELECT
[PersonId] = t.c.value('(../personid)[1]', 'NVARCHAR(50)')
,[Entertime] = t.c.value('.', 'NVARCHAR(50)')
FROM #x.nodes('root/person/entertime') t(c))
, cte_leavetime as (
SELECT
[PersonId] = t.c.value('(../personid)[1]', 'NVARCHAR(50)')
,[Leavetime] = t.c.value('.', 'NVARCHAR(50)')
FROM #x.nodes('root/person/leavetime') t(c))
SELECT
m.PersonID
,[First Name]
,[Last Name]
,[Entertime]
,[Leavetime]
FROM cte_maindata m
LEFT OUTER JOIN cte_entertime e on m.PersonId = e.PersonId
LEFT OUTER JOIN cte_leavetime l on m.PersonId = l.PersonId

Answer 3

Haven't realized you may have multiple persons in the document. My query would be incorrect in that case anyway. I thought maybe if you first shred out each person into its own XML fragment and ten extract the enter/leave times might perform better. I don't have 215k person XML to try, but here is an idea:
declare #x xml;
select #x = N'<root>
<person>
<personid>HH3269732</personid>
<firstname>John</firstname>
<lastname>Smith</lastname>
<entertime>01/02/2008 10:15</entertime>
<leavetime>01/02/2008 11:45</leavetime>
<entertime>03/01/2008 08:00</entertime>
<leavetime>03/01/2008 10:00</leavetime>
<entertime>04/01/2008 08:00</entertime>
</person>
<person>
<personid>HH3269733</personid>
<firstname>Jane</firstname>
<lastname>Doe</lastname>
<entertime>01/03/2008 10:15</entertime>
<leavetime>01/03/2008 11:45</leavetime>
<entertime>03/04/2008 08:00</entertime>
<leavetime>03/04/2008 10:00</leavetime>
<entertime>04/04/2008 08:00</entertime>
</person>
</root>';
with cte_person as (
select
t.c.value('(personid)[1]', 'NVARCHAR(50)') as personid
, t.c.value('(firstname)[1]', 'NVARCHAR(50)') as firstname
, t.c.value('(lastname)[1]', 'NVARCHAR(50)') as lastname
, t.c.query('entertime') as entertime
, t.c.query('leavetime') as leavetime
FROM #x.nodes('root/person') t(c))
, cte_cross_enter as (
select
p.personid
, p.firstname
, p.lastname
, x.c.value('.', 'datetime') as entertime
, row_number() over (partition by personid order by x.c) as row_enter
from cte_person p
cross apply p.entertime.nodes('/entertime') x(c))
, cte_cross_leave as (
select
p.personid
, x.c.value('.', 'datetime') as leavetime
, row_number() over (partition by personid order by x.c) as row_leave
from cte_person p
cross apply p.leavetime.nodes('/leavetime') x(c))
select e.personid
, e.firstname
, e.lastname
, e.entertime
, l.leavetime
from cte_cross_enter e
left outer join cte_cross_leave l
on e.personid = l.personid and
e.row_enter = l.row_leave