XPath : '/root[1]/value[1]' - , '/root[1]/value[2]' - .. '(/root/value)[1]' '(/root/value[2])'. , , 1, 2, 3 .. . , .
P.S. ?
declare @x xml = '<root>
<value>10</value>
<value>12</value>
<value>11</value>
<value>1</value>
<value>15</value>
<root>';
select x.value(N'position()', N'int') as position,
x.value(N'.', 'int') as value
from @x.nodes(N'//root/value') t(x)
, ...
Msg 2371, Level 16, State 1, Line 9
XQuery [value()]: 'position()' can only be used within a predicate or XPath selector
, ...