oracle中Blob、Clob、Varchar之间的互相转换

以下是oracle中Blob、Clob、Varchar之间的互相转换（都是百度找的，亲测可用）

Blob转Varchar2:

CREATE OR REPLACE FUNCTION blob_to_varchar (blob_in IN BLOB)
RETURN VARCHAR2
IS

v_varchar VARCHAR2(4000);
v_start PLS_INTEGER := 1;
v_buffer PLS_INTEGER := 4000;

BEGIN
 --select userenv('LANGUAGE') into g_nls_db_char from dual; 

 if DBMS_LOB.GETLENGTH(blob_in) is null then
        return empty_clob();
 end if;

 DBMS_OUTPUT.put_line('TEST:' || CEIL(DBMS_LOB.GETLENGTH(blob_in)));

 --DBMS_LOB.CREATETEMPORARY(v_clob, TRUE);

 FOR i IN 1..CEIL(DBMS_LOB.GETLENGTH(blob_in) / v_buffer)
 LOOP
--如果乱码了就需要调整字符集了 --select userenv('language') from dual 查看数据库编码
 v_varchar := UTL_RAW.CAST_TO_VARCHAR2(utl_raw.convert(DBMS_LOB.SUBSTR(blob_in, v_buffer, v_start),'SIMPLIFIED CHINESE_CHINA.ZHS16GBK', 'SIMPLIFIED CHINESE_CHINA.ZHS16GBK'));

 --DBMS_LOB.WRITEAPPEND(v_clob, LENGTH(v_varchar), v_varchar);

 v_start := v_start + v_buffer;
 END LOOP;

 --DBMS_OUTPUT.put_line(v_varchar);

 RETURN v_varchar;

end blob_to_varchar;

Blob转Clob:

CREATE OR REPLACE FUNCTION blob_to_clob (blob_in IN BLOB)
RETURN CLOB
IS
v_clob CLOB;
v_varchar VARCHAR2(4000);
v_start PLS_INTEGER := 1;
v_buffer PLS_INTEGER := 4000;
g_nls_db_char varchar2(60);
BEGIN
 select userenv('LANGUAGE') into g_nls_db_char from dual;

 if DBMS_LOB.GETLENGTH(blob_in) is null then
        return empty_clob();
 end if;

 DBMS_OUTPUT.put_line('TEST:' || CEIL(DBMS_LOB.GETLENGTH(blob_in)));

 DBMS_LOB.CREATETEMPORARY(v_clob, TRUE);

 FOR i IN 1..CEIL(DBMS_LOB.GETLENGTH(blob_in) / v_buffer)
 LOOP
--如果乱码了，就需要调整字符集了 select userenv('language') from dual --查看数据库编码
 v_varchar := UTL_RAW.CAST_TO_VARCHAR2(utl_raw.convert(DBMS_LOB.SUBSTR(blob_in, v_buffer, v_start),'SIMPLIFIED CHINESE_CHINA.ZHS16GBK','SIMPLIFIED CHINESE_CHINA.ZHS16GBK'));

 DBMS_LOB.WRITEAPPEND(v_clob, LENGTH(v_varchar), v_varchar);

 v_start := v_start + v_buffer;
 END LOOP;

 --DBMS_OUTPUT.put_line(v_varchar);

 RETURN v_clob;

end blob_to_clob;

Clob转Blob：

CREATE OR REPLACE FUNCTION Clob_To_Blob (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;
END Clob_To_Blob;

Clob转Varchar2 : to_char(CLOB)

Varchar2转Clob 自动隐式转化；

Varchar2转Blob：调用 Clob_To_Blob();