oracle中varchar2字段存入blob字段及blob转成varchar2

CREATE OR REPLACE FUNCTION C2B (b IN CLOB default empty_clob())
   RETURN BLOB
-- typecasts BLOB to CLOB (binary conversion)
IS
   res            BLOB;
   b_len          number  := dbms_lob.getlength(b) ;
   dest_offset1   NUMBER  := 1;
   src_offset1    NUMBER  := 1;
   amount_c       INTEGER := DBMS_LOB.lobmaxsize;
   blob_csid      NUMBER  := DBMS_LOB.default_csid;
   lang_ctx       INTEGER := DBMS_LOB.default_lang_ctx;
   warning        INTEGER;
BEGIN

   if  b_len  > 0  then
   DBMS_LOB.createtemporary (res, TRUE);
   DBMS_LOB.OPEN (res, DBMS_LOB.lob_readwrite);
   DBMS_LOB.convertToBlob (res,
                           b,
                           amount_c,
                           dest_offset1,
                           src_offset1,
                           blob_csid,
                           lang_ctx,
                           warning
                          );
 else
   select   empty_blob()  into  res  from  dual ;
  end if ;
   RETURN res;                                             -- res is OPEN here
END C2B;

 

1，首先利用to_clob函数把varchar2字段转成 clob字段。

2  利用上面函数将clob转成blob。

说白了就是  c2b(to_clob(varchar2字段))

create or replace Function Blob_To_Varchar (Blob_In In Blob) Return clob 
Is
    V_Varchar Varchar2(32767); 
     V_Varchar1 Varchar2(32767);
    V_Start Pls_Integer := 1; 
    V_Buffer Pls_Integer := 4000; 
Begin

    If Dbms_Lob.Getlength(Blob_In) Is Null Then
        Return '';
    End If;
    V_Varchar1 := '';
 --return to_char(Ceil(Dbms_Lob.Getlength(Blob_In) / V_Buffer));
    For I In 1..Ceil(Dbms_Lob.Getlength(Blob_In) / V_Buffer) Loop
        --当转换出来的字符串乱码时，可尝试用注释掉的函数
        --V_Varchar := Utl_Raw.Cast_To_Varchar2(Utl_Raw.Convert(Dbms_Lob.Substr(Blob_In, V_Buffer, V_Start),'SIMPLIFIED CHINESE_CHINA.ZHS16GBK', 'AMERICAN_THE NETHERLANDS.UTF8'));
        V_Varchar :=  Utl_Raw.Cast_To_Varchar2(Dbms_Lob.Substr(Blob_In, V_Buffer, V_Start));
        V_Varchar1 := V_Varchar1 || V_Varchar;
   
        V_Start := V_Start + V_Buffer; 
    End Loop;

    Return V_Varchar1;

End Blob_To_Varchar;

 

1.首先执行上面的函数，返回的是个clob

2将clob转成varchar2

说白了 就是    to_char(Blob_To_Varchar(字段))

创建二个函数 然后就可以用了，如果说实现 数据库里面大字段的批量替换还是比较方便

update DR_RPT_REPORT_DATASOURCE
set data_sql =
c2b(to_clob((select replace(Blob_To_Varchar(data_sql),'XXX','XXX') from DR_RPT_REPORT_DATASOURCE where data_id
='XXXX' ))) where data_id = '' ;

原文在这：http://blog.csdn.net/wbo112/article/details/9041575