操作ORACLE 数据库 的CLOB字段的问题

Question

  我在C#下访问ORACLE数据库。 读取数据。其中有个字段TEMP是CLOB类型。读取完后。发现有些记录的TEMP这个字段的值没有读取过来。请问下是为什么。我在网上找了下。有的说是CLOB存储的容量。在读取过来时超出了SQL的大小出现了问题。我对ORACLE不熟。请大家指点下。  如果能 给出 关于 CLOB类型的 读写方式更好。谢谢

Answer 1

/// <summary>
        /// 读取 Oracle Blob 到文件中。
        /// </summary>
        /// <param name="idData">id 值</param>
        /// <param name="fileName">文件名</param>
        /// <param name="id">id 键</param>
        /// <param name="blob">blob 键</param>
        /// <param name="tableName">表名</param>
        public void ReadBlob(int idData,string fileName, string id, string blob, string tableName)
        {
            string connString = "server=oratest;User ID=kttest;Password=test";
            using(conn = new OracleConnection(connString))
            {
                try
                {
                    conn.Open();
                    OracleCommand cmd = conn.CreateCommand();                    // 利用事务处理（必须）
                    OracleTransaction transaction = cmd.Connection.BeginTransaction();
                    cmd.Transaction = transaction;                    // 获得 OracleLob 指针
                    string sql = "select " + blob + " from " + tableName + " where " + id + " = " + idData;
                    cmd.CommandText = sql;
                    OracleDataReader dr = cmd.ExecuteReader();
                    dr.Read();
                    OracleLob tempLob = dr.GetOracleLob(0);
                    dr.Close();                    // 读取 BLOB 中数据，写入到文件中
                    FileStream fs = new FileStream(fileName,FileMode.Create);
                    int length = 1048576;
                    byte[] Buffer = new byte[length];
                    int i;
                    while((i = tempLob.Read(Buffer,0,length)) > 0)
                    {
                        fs.Write(Buffer,0,i);
                    }
                    fs.Close();
                    tempLob.Clone();
                    cmd.Parameters.Clear();                    // 提交事务
                    transaction.Commit();
                }
                catch(Exception ex)
                {
                    throw ex;
                }
                finally
                {
                    conn.Close();
                }
            }
        }

Answer 2

  OracleDataReader   reader   =   command.ExecuteReader();   
                  using(reader)   
                  {   
                          OracleLob   BLOB   =   reader.GetOracleLob(1)   
                          byte[]   buffer   =   System.Text.Encoding.Unicode.GetBytes(Content);   
                          if   (buffer.Length   <   BLOB.Length)   
                          {   
                                  BLOB.SetLength(buffer.Length)   
                          }   
                          BLOB.Write(buffer,0,buffer.Length);   
                          bReturn   =   true;   
                  }