T-SQL:当长度>时,如何比较两种类型的XML变量: VarChar(MAX)? [英] T-SQL: How can I compare two variables of type XML when length > VarChar(MAX)?
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问题描述
仅使用SQL Server 2008 R2(这将在存储过程中),我如何确定类型XML的两个变量是否等效?
Using only SQL Server 2008 R2 (this is going to be in a stored proc), how can I determine if two variables of type XML are equivalent?
是我想要做的:
DECLARE @XmlA XML
DECLARE @XmlB XML
SET @XmlA = '[Really long Xml value]'
SET @XmlB = '[Really long Xml value]'
IF @XmlA = @XmlB
SELECT 'Matching Xml!'
但是你可能知道,它返回:
But as you probably know, it returns:
Msg 305,Level 16,State 1,Line 7除非使用IS NULL运算符,否则XML数据类型不能为
比较或排序。
Msg 305, Level 16, State 1, Line 7 The XML data type cannot be compared or sorted, except when using the IS NULL operator.
我可以转换为 VarChar(MAX)
并比较,但只比较第一个2MB 。是否有其他方法?
I can convert to VarChar(MAX)
and compare, but that only compares the first 2MB. Is there another way?
推荐答案
检查此SQL函数:
CREATE FUNCTION [dbo].[CompareXml]
(
@xml1 XML,
@xml2 XML
)
RETURNS INT
AS
BEGIN
DECLARE @ret INT
SELECT @ret = 0
-- -------------------------------------------------------------
-- If one of the arguments is NULL then we assume that they are
-- not equal.
-- -------------------------------------------------------------
IF @xml1 IS NULL OR @xml2 IS NULL
BEGIN
RETURN 1
END
-- -------------------------------------------------------------
-- Match the name of the elements
-- -------------------------------------------------------------
IF (SELECT @xml1.value('(local-name((/*)[1]))','VARCHAR(MAX)'))
<>
(SELECT @xml2.value('(local-name((/*)[1]))','VARCHAR(MAX)'))
BEGIN
RETURN 1
END
---------------------------------------------------------------
--Match the value of the elements
---------------------------------------------------------------
IF((@xml1.query('count(/*)').value('.','INT') = 1) AND (@xml2.query('count(/*)').value('.','INT') = 1))
BEGIN
DECLARE @elValue1 VARCHAR(MAX), @elValue2 VARCHAR(MAX)
SELECT
@elValue1 = @xml1.value('((/*)[1])','VARCHAR(MAX)'),
@elValue2 = @xml2.value('((/*)[1])','VARCHAR(MAX)')
IF @elValue1 <> @elValue2
BEGIN
RETURN 1
END
END
-- -------------------------------------------------------------
-- Match the number of attributes
-- -------------------------------------------------------------
DECLARE @attCnt1 INT, @attCnt2 INT
SELECT
@attCnt1 = @xml1.query('count(/*/@*)').value('.','INT'),
@attCnt2 = @xml2.query('count(/*/@*)').value('.','INT')
IF @attCnt1 <> @attCnt2 BEGIN
RETURN 1
END
-- -------------------------------------------------------------
-- Match the attributes of attributes
-- Here we need to run a loop over each attribute in the
-- first XML element and see if the same attribut exists
-- in the second element. If the attribute exists, we
-- need to check if the value is the same.
-- -------------------------------------------------------------
DECLARE @cnt INT, @cnt2 INT
DECLARE @attName VARCHAR(MAX)
DECLARE @attValue VARCHAR(MAX)
SELECT @cnt = 1
WHILE @cnt <= @attCnt1
BEGIN
SELECT @attName = NULL, @attValue = NULL
SELECT
@attName = @xml1.value(
'local-name((/*/@*[sql:variable("@cnt")])[1])',
'varchar(MAX)'),
@attValue = @xml1.value(
'(/*/@*[sql:variable("@cnt")])[1]',
'varchar(MAX)')
-- check if the attribute exists in the other XML document
IF @xml2.exist(
'(/*/@*[local-name()=sql:variable("@attName")])[1]'
) = 0
BEGIN
RETURN 1
END
IF @xml2.value(
'(/*/@*[local-name()=sql:variable("@attName")])[1]',
'varchar(MAX)')
<>
@attValue
BEGIN
RETURN 1
END
SELECT @cnt = @cnt + 1
END
-- -------------------------------------------------------------
-- Match the number of child elements
-- -------------------------------------------------------------
DECLARE @elCnt1 INT, @elCnt2 INT
SELECT
@elCnt1 = @xml1.query('count(/*/*)').value('.','INT'),
@elCnt2 = @xml2.query('count(/*/*)').value('.','INT')
IF @elCnt1 <> @elCnt2
BEGIN
RETURN 1
END
-- -------------------------------------------------------------
-- Start recursion for each child element
-- -------------------------------------------------------------
SELECT @cnt = 1
SELECT @cnt2 = 1
DECLARE @x1 XML, @x2 XML
DECLARE @noMatch INT
WHILE @cnt <= @elCnt1
BEGIN
SELECT @x1 = @xml1.query('/*/*[sql:variable("@cnt")]')
--RETURN CONVERT(VARCHAR(MAX),@x1)
WHILE @cnt2 <= @elCnt2
BEGIN
SELECT @x2 = @xml2.query('/*/*[sql:variable("@cnt2")]')
SELECT @noMatch = dbo.CompareXml( @x1, @x2 )
IF @noMatch = 0 BREAK
SELECT @cnt2 = @cnt2 + 1
END
SELECT @cnt2 = 1
IF @noMatch = 1
BEGIN
RETURN 1
END
SELECT @cnt = @cnt + 1
END
RETURN @ret
END
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