注：下列过程中的参数p_filename为外部文件名称，p_name用于标识唯一的一行

1.创建目录utl_dir用于文件的导入、导出

create or replace directory utl_dir as 'd:\';

2.给所有用户赋予读写utl_dir的权限

grant write,read on directory utl_dir to public;

3.创建测试表blob_test，其中列a为blob类型，b列在实际应用中可以是表的PK列

create table blob_test(a blob,b number);

4.将外部文件插入blob列

CREATE OR REPLACE PROCEDURE insert_blob(p_name varchar2,p_filename varchar2) IS

i_blob BLOB;

i_file BFILE := BFILENAME('UTL_DIR',p_filename);

BEGIN

INSERT INTO blob_test VALUES (EMPTY_BLOB(),p_name)

RETURNING test INTO i_blob;

DBMS_LOB.FILEOPEN(i_file);

DBMS_LOB.LOADFROMFILE(i_blob, i_file, DBMS_LOB.GETLENGTH(i_file));

DBMS_LOB.FILECLOSE(i_file);

COMMIT;

END;

5.用外部文件更新blob列

CREATE OR REPLACE PROCEDURE update_blob(p_name varchar2,p_filename varchar2) IS

i_blob BLOB;

i_file BFILE := BFILENAME('UTL_DIR',p_filename);

BEGIN

UPDATE blob_test SET test = EMPTY_BLOB() WHERE b = p_name

RETURNING test INTO i_blob;

DBMS_LOB.FILEOPEN(i_file);

DBMS_LOB.LOADFROMFILE(i_blob, i_file, DBMS_LOB.GETLENGTH(i_file));

DBMS_LOB.FILECLOSE(i_file);

COMMIT;

END;

6.用于查看insert、update是否成功的语句

SELECT DBMS_LOB.GETLENGTH(test) FROM blob_test;

7.将数据库中的blob列导出为外部文件

CREATE OR REPLACE PROCEDURE dump_blob (p_name varchar2,p_filename varchar2) IS

l_file      UTL_FILE.FILE_TYPE;

l_buffer    RAW(32767);

l_amount    BINARY_INTEGER := 32767;

l_pos       INTEGER := 1;

l_blob      BLOB;

l_blob_len  INTEGER;

BEGIN

SELECT test INTO l_blob FROM blob_test WHERE b = p_name;

l_blob_len := DBMS_LOB.GETLENGTH(l_blob);

l_file := UTL_FILE.FOPEN('UTL_DIR',p_filename,'wb', 32767);

WHILE l_pos < l_blob_len LOOP

DBMS_LOB.READ (l_blob, l_amount, l_pos, l_buffer);

UTL_FILE.PUT_RAW(l_file, l_buffer, TRUE);

l_pos := l_pos + l_amount;

END LOOP;

UTL_FILE.FCLOSE(l_file);

EXCEPTION

WHEN OTHERS THEN

IF UTL_FILE.IS_OPEN(l_file) THEN

UTL_FILE.FCLOSE(l_file);

END IF;

RAISE;

END;