SQL Oracle如何提取blob列中的xml标记内容

Question

There is an xml that is in a column of type BLOB (in oracle) and I need to access a certain tag from that xml. Until then I can retrieve the column this way:

SELECT TRIM(UTL_RAW.CAST_TO_VARCHAR2(DBMS_LOB.SUBSTR(my_column_blob, 1024))) as tag_name_xml
FROM my_table

the return is like this:

Here I leave part of the xml content:

How do I return the value/content of the cUF or cCT tag? I would like the help of people with more knowledge, please.

the proposed solutions are very elegant, but for my case what would it be like to access with this xml structure to access the contents of the cUF tag?

<?xml version="1.0" encoding="UTF-8"?>
<cteProc xmlns="http://www.example.com" version="3.00">
   <CTe>
      <infCte version="3.00">
         <ide>
            <cUF>15</cUF>
         </ide>
      </infCte>
   </CTe>
</cteProc>

Answer 1

You can first convert your BLOB data into CLOB type, and then extract the tags you need. Here are two functions that will, hopefully, solve your problem:

FUNCTION BLOB2CLOB(mBLOB IN BLOB) 
    RETURN CLOB IS
BEGIN
    Declare
        mCLOB   CLOB;
        mDestOffSet     INTEGER;
        mSrcOffSet      INTEGER;
        mBLOBCSID       INTEGER;
        mLangCntx       INTEGER;
        mWarn           INTEGER;
    Begin
        mDestOffSet := 1;
        mSrcOffSet := 1;
        mBLOBCSID := 0;
        mLangCntx := 0;
        mWarn := 0;
        DBMS_LOB.CreateTemporary(mCLOB, TRUE);
        DBMS_LOB.ConvertToClob(mCLOB, mBLOB, DBMS_LOB.GetLength(mBLOB), mDestOffSet, mSrcOffSet, mBLOBCSID, mLangCntx, mWarn);
        RETURN(mCLOB);
    End;
END BLOB2CLOB;
--
FUNCTION Get_SOAP_PartCLOB(mCLOB IN CLOB, mTag IN VARCHAR2) RETURN CLOB 
  IS
BEGIN
    Declare
        wrkCLOB         CLOB;
    myStart       NUMBER(10) := 0;
    myEnd         NUMBER(10) := 0;
    myLength      NUMBER(10) := 0;
    toErase       NUMBER(10) := 0;
    Begin
    DBMS_LOB.CreateTemporary(wrkCLOB, True);
    DBMS_LOB.COPY(wrkCLOB, mCLOB, DBMS_LOB.GETLENGTH(mCLOB));
    --
    myStart := DBMS_LOB.InStr(wrkCLOB, mTag, 1, 1) + Length(mTag) - 1;
    myEnd := DBMS_LOB.InStr(wrkCLOB, SubStr(mTag, 1, 1) || '/' || SubStr(mTag, 2));
    myLength := DBMS_LOB.GetLength(wrkCLOB);
    
    DBMS_LOB.ERASE(wrkCLOB, myStart, 1);
    toErase := myLength - myEnd + 1;

    DBMS_LOB.ERASE(wrkCLOB, toErase, myEnd);
    
    wrkCLOB := REPLACE(wrkCLOB, ' ', '');

        RETURN(wrkCLOB);
    End;
END Get_SOAP_PartCLOB;

You can use it like this:

SELECT 
    Get_SOAP_PartCLOB(BLOB2CLOB(YOUR_BLOB_COL), 'your_tag_in_clob') as "TAG_COL_ALIAS"
FROM
    YOUR_TABLE

I use the second function Get_SOAP_PartCLOB() to get some pretty big B64 data out of the soap envelope response from certain web services. That's why the return type is CLOB. You can cast the returned value to something else or make your own adjustments to the function.

Answer 2

Use XMLTYPE and XMLTABLE :

SELECT x.c
FROM   table_name t
       CROSS JOIN XMLTABLE(
         '/a/b/c'
         PASSING XMLTYPE(t.value, 1)
         COLUMNS
           c VARCHAR2(200) PATH './text()'
       ) x;

Or XMLQUERY :

SELECT XMLQUERY('/a/b/c/text()' PASSING XMLTYPE(value, 1) RETURNING CONTENT) AS c
FROM   table_name

Which, for the sample data:

CREATE TABLE table_name (value BLOB);

INSERT INTO table_name (value)
VALUES ( UTL_RAW.CAST_TO_RAW( '<a><b><c>something</c></b></a>' ) );

Both output:

C
something

db<>fiddle here