CUBRID学习笔记 15 Lobs类型数据

• BLOB: Binary large object
• CLOB: Character large object 
• 一个二进制 一个字符类型

 

  二进制的读取

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CUBRIDCommand cmd = new CUBRIDCommand(sql, conn);

DbDataReader reader = cmd.ExecuteReader();

while (reader.Read())

{

    CUBRIDBlob bImage = (CUBRIDBlob)reader[0];

    byte[] bytes = new byte[(int)bImage.BlobLength];

    bytes = bImage.getBytes(1, (int)bImage.BlobLength);

    //...

}<br><br><br>更新  clob类型

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string sql = "UPDATE t SET c = ?";

CUBRIDCommand cmd = new CUBRIDCommand(sql, conn);

 

CUBRIDClob Clob = new CUBRIDClob(conn);

 

//Use the ConnectionString for testing

str = "server=localhost;database=demodb;port=33000;user=public;password="

 

Clob.setString(1, str);

CUBRIDParameter param = new CUBRIDParameter();

param.ParameterName = "?";

param.CUBRIDDataType = CUBRIDDataType.CCI_U_TYPE_CLOB;

param.Value = Clob;

cmd.Parameters.Add(param);

cmd.ExecuteNonQuery();

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<br>下面来看个完整的例子

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using CUBRID.Data.CUBRIDClient;

using System.Diagnostics;

using System;

using System.IO;

using System.Data.Common;

 

namespace LobExample

{

    class Program

    {

        private static void ExecuteSQL(string sql, CUBRIDConnection conn)

        {

            using (CUBRIDCommand cmd = new CUBRIDCommand(sql, conn))

            {

                cmd.ExecuteNonQuery();

            }

        }

 

        private static void CreateTestTableLOB(CUBRIDConnection conn)

        {

            ExecuteSQL("drop table if exists t", conn);

            ExecuteSQL("create table t(b BLOB, c CLOB)", conn);

        }

 

        private static void CleanupTestTableLOB(CUBRIDConnection conn)

        {

            ExecuteSQL("drop table if exists t", conn);

        }

 

        static void Main(string[] args)

        {

            CUBRIDConnectionStringBuilder sb = new CUBRIDConnectionStringBuilder("localhost", "demodb", "public", "", "33000");

            using (CUBRIDConnection conn = new CUBRIDConnection(sb.GetConnectionString()))

            {

                conn.Open();

 

                CreateTestTableLOB(conn);

 

                string sql = "insert into t (c) values(?)";

                CUBRIDCommand cmd = new CUBRIDCommand(sql, conn);

 

                CUBRIDClob Clob = new CUBRIDClob(conn);

 

                String str = conn.ConnectionString;

 

                StreamReader r = new StreamReader("test.txt");

                string writestring = r.ReadToEnd();

                r.Close();

 

                Clob.setString(1, writestring);

 

                CUBRIDParameter param = new CUBRIDParameter();

                param.ParameterName = "?";

                param.CUBRIDDataType = CUBRIDDataType.CCI_U_TYPE_CLOB;

                param.Value = Clob;

                cmd.Parameters.Add(param);

                cmd.ExecuteNonQuery();

                cmd.Close();

 

                string sql2 = "SELECT c from t";

                using (CUBRIDCommand cmd2 = new CUBRIDCommand(sql2, conn))

                {

                    DbDataReader reader = cmd2.ExecuteReader();

 

                    while (reader.Read())

                    {

                        CUBRIDClob cImage = (CUBRIDClob)reader[0];

                        string str2 = cImage.getString(1, (int)cImage.ClobLength);

 

                        StreamWriter w = new StreamWriter("testout.txt");

                        w.Write(str2);

                        w.Close();

 

                        StreamReader r2 = new StreamReader("testout.txt");

                        string readstring = r2.ReadToEnd();

                        r2.Close();

 

                        Debug.Assert(writestring.Length == readstring.Length, "The inserted CLOB length is not valid!");

                        Debug.Assert(writestring.Equals(readstring), "The CLOB was not inserted correctly!");

                    }

                }

 

                CleanupTestTableLOB(conn);

 

                conn.Close();

            }

        }

    }

}

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