SQL 2012 - iterate through an XML list (better alternative to a WHILE loop)

问题

Using SQL 2012 & getting XML passed into a stored procedure that must take that input & write a row to the table for each of the items that is in a section of the XML that is passed to the stored procedure. The XML looks like:

<MyXML>
    <MyMsg>My Text Message</MyMsg>
    <MsgTime>2013-09-25 10:52:37.098</MsgTime>
    <SendToList>
    <SendTo>John</SendTo>
    <SendTo>James</SendTo>
    <SendTo>Rob</SendTo>
    <SendTo>Pete</SendTo>
    <SendTo>Sam</SendTo>
    </SendToList>
</MyXML>

The output of the stored procedure should be 5 rows inserted into a table (one for each SendTo above), and each having the same value in the MyMsg and MsgTime fields in that table.

I can get the count of the number of SendTo and can get the XML SendToList but I don't know how to iterate through it to do the inserts.

I can use the following SQL to get what's in the XML.

SELECT 
x.value('(/MyXML/MyMsg)[1]', 'VARCHAR(1024)'),
x.value('(/MyXML/MsgTime)[1]', 'DATETIME'),
   @max = x.query('<e> { count(/MyXML/SendToList/SendTo) } </e>').value('e[1]','int'),
   @mlst = x.query('/MyXML/SendTo')
    FROM @XML_In.nodes('//MyXML') i(x)

Currently, I'm using variables and a WHILE to loop through the items in the SendToList, but I know there's got to be a better way.

SELECT @msgTo= @XML_In.value('(/MyXML/SendToList/SendTo[position()=sql:variable("@cnt")])[1]','VARCHAR(100)')

The above gets me the value of each item in the SendToList.
If I select the variable @mlst, I can see the structure of the XML that I need to loop through.

<SendToList>
   <SendTo>John</SendTo>
   <SendTo>James</SendTo>
   <SendTo>Rob</SendTo>
   <SendTo>Pete</SendTo>
   <SendTo>Sam</SendTo>
</SendToList>

Even though the WHILE works, it's doing one insert right after the other. I was thinking that the methods available should be able to do it all instead of looping but I don't know enough about using them to do what I need to do.

Would appreciate any help or suggestions.

回答1:

If you need to do to something that requires a loop (for example, you want to send email to each recipient, than you can use a cursor:

declare cur cursor local fast_forward for
    select
        s.c.value('(text())[1]', 'nvarchar(max)') as SendTo,
        m.c.value('(MyMsg/text())[1]', 'nvarchar(max)') as MyMsg,
        m.c.value('(MsgTime/text())[1]', 'nvarchar(max)') as MsgTime
    from @XML_In.nodes('MyXML') as m(c)
        outer apply m.c.nodes('SendToList/SendTo') as s(c)

open cur
while 1 = 1
begin
    fetch cur into @SendTo, @MyMsg, @MsgTime
    if @@fetch_status <> 0 break

    --=======================================
    -- do what you need here 
    --=======================================
end
close cur
deallocate cur

If you just want to insert rows into some table, you can do this in one simple insert:

insert into <Your table>
(
    SendTo, MyMsg, MsgTime
)
select
    s.c.value('(text())[1]', 'nvarchar(max)') as SendTo,
    m.c.value('(MyMsg/text())[1]', 'nvarchar(max)') as MyMsg,
    m.c.value('(MsgTime/text())[1]', 'nvarchar(max)') as MsgTime
from @XML_In.nodes('MyXML') as m(c)
    outer apply m.c.nodes('SendToList/SendTo') as s(c)

sql fiddle demo

来源：https://stackoverflow.com/questions/19034382/sql-2012-iterate-through-an-xml-list-better-alternative-to-a-while-loop

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sql

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xml

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sqlxml