XQuery：使用 if 语句时删除 xml 声明

Question

考虑以下三个陈述。

1：

XMLSERIALIZE(DOCUMENT XMLQUERY(q'^
                                copy $i := $doc modify (
                                    for $j in $i/tdfmt/text()[1]
                                return 
                                    insert node ( $text, $br, '
' ) before $j
                                )
                                return $i
                               ^'
        PASSING
            XMLTYPE(OIT.INFTXT)  AS "doc",
            LENGTH(EXTRACTVALUE(XMLTYPE(OIT.INFTXT),'tdfmt/text()[1]')) AS "len",
            'NEW TEXT TO INSERT' AS "text",
            XMLTYPE('<br/>')            AS "br"
        RETURNING CONTENT)  AS CLOB INDENT SIZE=4 )
        AS NEW_INFTXT_A

2：

XMLSERIALIZE(DOCUMENT XMLQUERY(q'^
                                copy $i := $doc modify (
                                    for $j in $i/*
                                return 
                                    insert node ( $text, $br, '
' ) into $j
                                )
                                return $i
                               ^'
        PASSING
            XMLTYPE(OIT.INFTXT)  AS "doc",
            LENGTH(EXTRACTVALUE(XMLTYPE(OIT.INFTXT),'tdfmt/text()[1]')) AS "len",
            'NEW TEXT TO INSERT' AS "text",
            XMLTYPE('<br/>')            AS "br"
        RETURNING CONTENT)  AS CLOB INDENT SIZE=4 )
        AS NEW_INFTXT_B

3：

XMLSERIALIZE(DOCUMENT XMLQUERY(q'^                                      
                                if ($len>0) 
                                then    
                                    copy $i := $doc modify (
                                        for $j in $i/tdfmt/text()[1]
                                    return 
                                        insert node ( $text, $br, '
' ) before $j
                                    )
                                    return $i
                                else    
                                    copy $i := $doc modify (
                                        for $j in $i/*
                                    return 
                                        insert node ( $text, $br, '
' ) into $j
                                    )
                                    return $i
                               ^'
        PASSING
            XMLTYPE(OIT.INFTXT)  AS "doc",
            LENGTH(EXTRACTVALUE(XMLTYPE(OIT.INFTXT),'tdfmt/text()[1]')) AS "len",
            'NEW TEXT TO INSERT' AS "text",
            XMLTYPE('<br/>')            AS "br"
        RETURNING CONTENT)  AS CLOB INDENT SIZE=4 )
        AS NEW_INFTXT1

这个想法是根据节点的长度在 1 和 2 之间切换。 在 3 的输出中，我注意到 xml 声明

<?xml version="1.0"?>

被省略，而 1 和 2 则存在。知道为什么添加

if then else

声明会导致这种行为，以及我应该采取什么措施来防止声明表被删除。

Answer 1

不确定为什么会产生这种效果，但您可以通过将

if

放在

modify

内来避免这种情况：

SELECT XMLSERIALIZE(DOCUMENT XMLQUERY(q'^                                      
                                copy $i := $doc modify (
                                    if ($len>0) 
                                    then    
                                        for $j in $i/tdfmt/text()[1]
                                        return 
                                        insert node ( $text, $br, '
' ) before $j
                                    else    
                                        for $j in $i/*
                                        return 
                                        insert node ( $text, $br, '
' ) into $j
                                )
                                return $i
                               ^'
        PASSING
            XMLTYPE(OIT.INFTXT)  AS "doc",
            LENGTH(EXTRACTVALUE(XMLTYPE(OIT.INFTXT),'tdfmt/text()[1]')) AS "len",
            'NEW TEXT TO INSERT' AS "text",
            XMLTYPE('<br/>')            AS "br"
        RETURNING CONTENT)  AS CLOB INDENT SIZE=4 )
        AS NEW_INFTXT1
FROM OIT

NEW_INFTXT1
要插入新文本 31 05 2022 Rico Strydom Op verzoek（zie电子邮件）保证overplaatsen....      超额预订信用证： 银行代码：1171 T.L .V.：VERP。 NL99BANK999999999999 T.G.V.：RC NL00BANK000000000000 BEDRAG：欧元9999999 BESCHRIJVING：Vrijgave verpandingcreditgelden AA98987987987 ivm overzetten zekerheid naar BGF
要插入新文本

小提琴