我想通过pl/sql程序将excel作为邮件附件发送。

DECLARE
   l_mailhost     VARCHAR2 (255) := 'smtp.example.com'; -- 邮件服务器主机名
   l_mailport     NUMBER := 25; -- 邮件服务器端口号
   l_from         VARCHAR2 (255) := 'sender@example.com'; -- 发件人邮箱
   l_to           VARCHAR2 (255) := 'recipient@example.com'; -- 收件人邮箱
   l_subject      VARCHAR2 (255) := '邮件主题'; -- 邮件主题
   l_message      VARCHAR2 (4000) := '邮件正文'; -- 邮件正文
   l_attachment   BLOB; -- 附件内容
   l_filename     VARCHAR2 (255) := 'attachment.xlsx'; -- 附件文件名
   l_connection   UTL_SMTP.connection;
   l_buffer       RAW (32767);
   l_amount       BINARY_INTEGER := 32767;
   l_pos          INTEGER := 1;
   l_bloblen      INTEGER;
BEGIN
   -- 读取Excel文件内容到BLOB
   SELECT attachment INTO l_attachment
     FROM your_table
    WHERE attachment_name = l_filename;

   -- 创建SMTP连接
   l_connection := UTL_SMTP.open_connection (l_mailhost, l_mailport);
   UTL_SMTP.helo (l_connection, l_mailhost);
   UTL_SMTP.mail (l_connection, l_from);
   UTL_SMTP.rcpt (l_connection, l_to);

   -- 开始邮件内容
   UTL_SMTP.open_data (l_connection);
   UTL_SMTP.write_data (l_connection, 'Date: ' || TO_CHAR (SYSDATE, 'DD-MON-YYYY HH24:MI:SS') || UTL_TCP.crlf);
   UTL_SMTP.write_data (l_connection, 'From: ' || l_from || UTL_TCP.crlf);
   UTL_SMTP.write_data (l_connection, 'Subject: ' || l_subject || UTL_TCP.crlf);
   UTL_SMTP.write_data (l_connection, 'To: ' || l_to || UTL_TCP.crlf);
   UTL_SMTP.write_data (l_connection, 'MIME-Version: 1.0' || UTL_TCP.crlf);
   UTL_SMTP.write_data (l_connection, 'Content-Type: multipart/mixed; boundary="SECBOUND"' || UTL_TCP.crlf || UTL_TCP.crlf);

   -- 邮件正文
   UTL_SMTP.write_data (l_connection, '--SECBOUND' || UTL_TCP.crlf);
   UTL_SMTP.write_data (l_connection, 'Content-Type: text/plain; charset="UTF-8"' || UTL_TCP.crlf || UTL_TCP.crlf);
   UTL_SMTP.write_data (l_connection, l_message || UTL_TCP.crlf || UTL_TCP.crlf);

   -- 附件
   UTL_SMTP.write_data (l_connection, '--SECBOUND' || UTL_TCP.crlf);
   UTL_SMTP.write_data (l_connection, 'Content-Type: application/vnd.openxmlformats-officedocument.spreadsheetml.sheet' || UTL_TCP.crlf);
   UTL_SMTP.write_data (l_connection, 'Content-Disposition: attachment; filename="' || l_filename || '"' || UTL_TCP.crlf || UTL_TCP.crlf);

   -- 附件内容
   l_bloblen := DBMS_LOB.getlength (l_attachment);
   WHILE l_pos < l_bloblen
   LOOP
      DBMS_LOB.read (l_attachment, l_amount, l_pos, l_buffer);
      UTL_SMTP.write_raw_data (l_connection, l_buffer, l_amount);
      l_pos := l_pos + l_amount;
   END LOOP;

   -- 结束邮件内容
   UTL_SMTP.write_data (l_connection, UTL_TCP.crlf || UTL_TCP.crlf || '--SECBOUND--');
   UTL_SMTP.close_data (l_connection);

   -- 发送邮件
   UTL_SMTP.quit (l_connection);
END;