问题描述
我的 xml 看起来像这样：
<items>
<item>
<itemproperty>true</itemproperty>
<details>
<details>
<ID Type="z" Value="1"/>
<ID Type="w" Value="2"/>
</details>
</Locations>
</item>
<item>
<itemproperty>true</itemproperty>
<details>
<details>
<ID Type="a" Value="3"/>
<ID Type="b" Value="4"/>
</details>
</Locations>
</item>
</items>
我想产生这样的输出：
ItemIndex DetailIDType DetailIDValue
1 z 1
1 w 2
2 a 3
2 b 4
我从 /items/item/details/detail/ID 节点查询并尝试找出祖先项元素的位置/索引。我可以获得 item 元素的总数，但我很难找到 item 元素的位置。在所有情况下，它都没有返回正确的索引/位置值：
SELECT DISTINCT
[TestGetItemElementName] = IDs.id.value('fn:local-name(./../../..)','varchar(50)'),[TestGetItemElementCount] = IDs.id.value('count(/items/item)','int'),[ItemIndexTest1] = IDs.id.value('for $i in ./../../.. return count(/items/item/*[. << $i]) + 1',[ItemIndexTest2] = IDs.id.value('for $i in . return count(../*[. << $i]) + 1',[DetailIDType] = convert(VARCHAR(256),IDs.id.query('data(./@Type)')),[DetailIDValue] = convert(VARCHAR(256),IDs.id.query('data(./@Value)'))
FROM
@x.nodes('/Recipients/Recipient/Locations/Location/ID') AS IDs(id)
解决方法
尽量避免在 XPath 查询中使用父轴（.. 或 parent::node()），因为它会严重影响性能。
您可以通过使用 DENSE_RANK() 来提供 item 节点的自动编号，并使用如下代码实现您要查找的内容...
declare @x xml = N'<items>
<item>
<itemproperty>true</itemproperty>
<Locations>
<details>
<ID Type="z" Value="1"/>
<ID Type="w" Value="2"/>
</details>
</Locations>
</item>
<item>
<itemproperty>true</itemproperty>
<Locations>
<details>
<ID Type="a" Value="3"/>
<ID Type="b" Value="4"/>
</details>
</Locations>
</item>
</items>';
select
dense_rank() over (partition by items order by item) as ItemIndex,details.value('@Type',N'nvarchar(256)') as DetailIDType,details.value('@Value',N'nvarchar(256)') as DetailIDValue
from @x.nodes('//items') nodes1(items)
cross apply items.nodes('item') nodes2(item)
cross apply item.nodes('Locations/details/ID') nodes3(details);
产生的结果：
| ItemIndex | DetailIDType | DetailIDValue |
|---|---|---|
| 1 | z | 1 |
| 1 | w | 2 |
| 2 | 一 | 3 |
| 2 | b | 4 |
我看到您尝试使用 节点比较 运算符来获取 ItemIndex 列值。以下是正确操作的方法。
SQL
>readelf -S app
There are 27 section headers,starting at offset 0x270:
Section Headers:
[Nr] Name Type Address Offset
Size EntSize Flags Link Info Align
[ 0] NULL 0000000000000000 00000000
0000000000000000 0000000000000000 0 0 0
[ 1] .text PROGBITS 0000000000401000 00001000
000000000223c47d 0000000000000000 AX 0 0 16
[ 2] .plt PROGBITS 000000000263d480 0223d480
0000000000000290 0000000000000010 AX 0 0 16
[ 3] .rodata PROGBITS 000000000263e000 0223e000
0000000000cd4919 0000000000000000 A 0 0 32
[ 4] .rela RELA 0000000003312920 02f12920
0000000000000018 0000000000000018 A 11 0 8
[ 5] .rela.plt RELA 0000000003312938 02f12938
00000000000003c0 0000000000000018 A 11 2 8
[ 6] .gnu.version_r VERNEED 0000000003312d00 02f12d00
0000000000000050 0000000000000000 A 10 2 8
[ 7] .gnu.version VERSYM 0000000003312d60 02f12d60
000000000000005a 0000000000000002 A 11 0 2
[ 8] .hash HASH 0000000003312dc0 02f12dc0
00000000000000d8 0000000000000004 A 11 0 8
[ 9] .shstrtab STRTAB 0000000000000000 02f12ea0
0000000000000111 0000000000000000 0 0 1
[10] .dynstr STRTAB 0000000003312fc0 02f12fc0
0000000000000268 0000000000000000 A 0 0 1
[11] .dynsym DYNSYM 0000000003313240 02f13240
0000000000000438 0000000000000018 A 10 1 8
[12] .typelink PROGBITS 0000000003313680 02f13680
000000000001064c 0000000000000000 A 0 0 32
[13] .itablink PROGBITS 0000000003323cd0 02f23cd0
0000000000006a60 0000000000000000 A 0 0 8
[14] .gosymtab PROGBITS 000000000332a730 02f2a730
0000000000000000 0000000000000000 A 0 0 1
[15] .gopclntab PROGBITS 000000000332a740 02f2a740
000000000113d450 0000000000000000 A 0 0 32
[16] .go.buildinfo PROGBITS 0000000004468000 04068000
0000000000000020 0000000000000000 WA 0 0 16
[17] .dynamic DYNAMIC 0000000004468020 04068020
0000000000000130 0000000000000010 WA 10 0 8
[18] .got.plt PROGBITS 0000000004468160 04068160
0000000000000158 0000000000000008 WA 0 0 8
[19] .got PROGBITS 00000000044682b8 040682b8
0000000000000008 0000000000000008 WA 0 0 8
[20] .noptrdata PROGBITS 00000000044682c0 040682c0
00000000000885c0 0000000000000000 WA 0 0 32
[21] .data PROGBITS 00000000044f0880 040f0880
000000000001f630 0000000000000000 WA 0 0 32
[22] .bss NOBITS 000000000450fec0 0410fec0
000000000003ba90 0000000000000000 WA 0 0 32
[23] .noptrbss NOBITS 000000000454b960 0414b960
0000000000004708 0000000000000000 WA 0 0 32
[24] .tbss NOBITS 0000000000000000 00000000
0000000000000008 0000000000000000 WAT 0 0 8
[25] .interp PROGBITS 0000000000400fe4 00000fe4
000000000000001c 0000000000000000 A 0 0 1
[26] .note.go.buildid NOTE 0000000000400f80 00000f80
0000000000000064 0000000000000000 A 0 0 4
Key to Flags:
W (write),A (alloc),X (execute),M (merge),S (strings),I (info),L (link order),O (extra OS processing required),G (group),T (TLS),C (compressed),x (unknown),o (OS specific),E (exclude),l (large),p (processor specific)
输出
DECLARE @x XML =
N'<items>
<item>
<itemproperty>true</itemproperty>
<Locations>
<details>
<ID Type="z" Value="1"/>
<ID Type="w" Value="2"/>
</details>
</Locations>
</item>
<item>
<itemproperty>true</itemproperty>
<Locations>
<details>
<ID Type="a" Value="3"/>
<ID Type="b" Value="4"/>
</details>
</Locations>
</item>
</items>';
SELECT c.value('for $i in . return count(/items/item[. << $i])','INT') AS ItemIndex,c.value('@Type','VARCHAR(20)') as DetailIDType,c.value('@Value','INT') as DetailIDValue
FROM @x.nodes('/items/item/Locations/details/ID') AS t(c);
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