C#:SqlServer操作的知识点

 

 

1、检查数据库连接的有效性



	var client = new System.Net.Sockets.TcpClient();

 	var ar = client.BeginConnect(host, 1433, null, null);

        ar.AsyncWaitHandle.WaitOne(500);

        return client.Connected;



	client.Close();	





2、检查连接字符串是否可以连接数据库



	SqlConnection _connection; 



	if (_connection == null)

                {

                    _connection = new SqlConnection(ConnectionString);

                    _connection.Open();

                }

                else if (_connection.State == System.Data.ConnectionState.Closed)

                {

                    _connection.Open();

                }

                else if (_connection.State == System.Data.ConnectionState.Broken)

                {

                    _connection.Close();

                    _connection.Open();

                }

                return _connection;	





3、判断是否存在某表的某个字段



	string sql = "select count(1) from syscolumns where [id]=object_id('" + tableName + "') and [name]='" + columnName + "'";



	using (SqlCommand cmd = new SqlCommand(sql , Connection))

                {

                    object obj = cmd.ExecuteScalar();

                    if ((Object.Equals(obj, null)) || (Object.Equals(obj, System.DBNull.Value)))

                    {

                        return null;

                    }

                    else

                    {

                        return obj;

                    }

                }

	

	Connection.Close();





4、执行查询语句，返回SqlDataReader ( 注意：调用该方法后，一定要对SqlDataReader进行Close )



 	SqlCommand cmd = new SqlCommand(strSQL, Connection);

	SqlDataReader reader= cmd.ExecuteReader(CommandBehavior.CloseConnection);



                if (reader.Read())

                {

                    reader["columnName"].ToString();

                }



                reader.Close();



	Connection.Close();



5、执行查询语句，返回DataSet



	DataSet ds = new DataSet();

	SqlDataAdapter command = new SqlDataAdapter(SQLString, Connection);

        command.Fill(ds, "ds");



	Connection.Close();





6、 执行SQL语句，返回影响的记录数



	SqlCommand cmd = new SqlCommand();



	if (conn.State != ConnectionState.Open)

	{

        	conn.Open();

	}

        cmd.Connection = conn;

        cmd.CommandText = sql;

        if (trans != null)

	{			

        	cmd.Transaction = trans;

	}

        cmd.CommandType = CommandType.Text;//cmdType;

        if (cmdParms != null)

        {

                foreach (SqlParameter parameter in cmdParms)

                {

                    if ((parameter.Direction == ParameterDirection.InputOutput || parameter.Direction == ParameterDirection.Input) &&

                        (parameter.Value == null))

                    {

                        parameter.Value = DBNull.Value;

                    }

                    cmd.Parameters.Add(parameter);

         	}

         }



	int rows = cmd.ExecuteNonQuery();

        cmd.Parameters.Clear();

        return rows;



	conn.Close();





7、批量复制数据、插入数据，实现数据库事务





	if (conn.State != ConnectionState.Open)

        {

         	conn.Open();

        }



	SqlTransaction trans = conn.BeginTransaction();



	//定义批量处理对象

            SqlBulkCopy bulkCopy = new SqlBulkCopy(conn, SqlBulkCopyOptions.KeepIdentity, trans);



            foreach (DataColumn item in dataTable.Columns)

            {

                bulkCopy.ColumnMappings.Add(item.ColumnName, item.ColumnName);

            }



            //指定被操作的数据表名

            bulkCopy.DestinationTableName = tableName;



            bulkCopy.BatchSize = size;

            bulkCopy.BulkCopyTimeout = 50;



	

            //数据插入到数据库

            bulkCopy.WriteToServer(dataTable);

            bulkCopy.Close();

	    bool isSuccess = ture;



            if (isSuccess)

            {

                trans.Commit();

            }

            else

            {

                trans.Rollback();

            }





8、执行存储过程



 	    DataSet dataSet = new DataSet();

            SqlDataAdapter sqlDA = new SqlDataAdapter();



	    SqlCommand command = new SqlCommand(storedProcName, connection);

            command.CommandType = CommandType.StoredProcedure;

            foreach (SqlParameter parameter in parameters)

            {

                if (parameter != null)

                {

                    // 检查未分配值的输出参数,将其分配以DBNull.Value.

                    if ((parameter.Direction == ParameterDirection.InputOutput || parameter.Direction == ParameterDirection.Input) &&

                        (parameter.Value == null))

                    {

                        parameter.Value = DBNull.Value;

                    }

                    command.Parameters.Add(parameter);

                }

            }



	    sqlDA.SelectCommand = command;

 	    //sqlDA.SelectCommand.CommandTimeout = Times;

            sqlDA.Fill(dataSet, tableName);

            Connection.Close();



	//command.Parameters.Add(new SqlParameter("ReturnValue",

                SqlDbType.Int, 4, ParameterDirection.ReturnValue,

                false, 0, 0, string.Empty, DataRowVersion.Default, null));

	//rowsAffected = command.ExecuteNonQuery();

	//result = (int)command.Parameters["ReturnValue"].Value;





9、备份数据库



	    SqlCommand command = new SqlCommand("use master;backup database @name to disk=@path;", Connection);

            command.Parameters.AddWithValue("@name", dbName);

            command.Parameters.AddWithValue("@path", pathDB);

            //command.Parameters.AddWithValue("@pathLog",pathLog);

            num = command.ExecuteNonQuery();

            Connection.Close();





10、恢复sql server数据库



	    SqlCommand command = new SqlCommand("use master;restore database @name from disk=@path WITH replace;", Connection);

            command.Parameters.AddWithValue("@name", dbName);

            command.Parameters.AddWithValue("@path", pathDB);

            //command.Parameters.AddWithValue("@pathLog",pathLog);

            num = command.ExecuteNonQuery();

            Connection.Close();





11、加载Excel   



 

		string strConn;

                strConn = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" + filePath + ";Extended Properties='Excel 8.0;HDR=False;IMEX=1'";

                OleDbConnection OleConn = new System.Data.OleDb.OleDbConnection(strConn);

                OleConn.Open();



                System.Data.DataTable sheetNames = OleConn.GetOleDbSchemaTable(System.Data.OleDb.OleDbSchemaGuid.Tables, new object[] { null, null, null, "TABLE" });//获得Excel



表的架构信息





                String sql = "SELECT * FROM  [" + sheetNames.Rows[0]["TABLE_NAME"] + "]";//可是更改Sheet名称，比如sheet2，等等    



                OleDbDataAdapter OleDaExcel = new OleDbDataAdapter(sql, OleConn);

                DataSet OleDsExcle = new DataSet();

                OleDaExcel.Fill(OleDsExcle);

                OleConn.Close();

                return OleDsExcle;

 特别操作

1、获取全部数据库名称



　　　　　　  ArrayList DBNameList = new ArrayList();

            SqlConnection Connection = new SqlConnection(String.Format("Data Source={0};Initial Catalog=master;User ID={1};PWD={2}", DSN, UID, PWD));

            DataTable DBNameTable = new DataTable();

            SqlDataAdapter Adapter = new SqlDataAdapter("select name from master..sysdatabases", Connection);

            Adapter.Fill(DBNameTable);



            foreach (DataRow Row in DBNameTable.Rows)

            {

                DBNameList.Add(Row[0]);

            }





2、得到指定数据库中的全部表名称



　　　　      string constr = String.Format("Data Source={0};Initial Catalog={1};User ID={2};PWD={3}", DSN, dbname, UID, PWD);

            SqlConnection myConnection = new SqlConnection(constr);

            //根据选中数据库，得到相应的所有表 

            string strSQL = "select name from sysobjects where type='" + 'U' + "'";

            DataSet ds = new DataSet();

            SqlDataAdapter myCommand = new SqlDataAdapter(strSQL, myConnection);

            myCommand.Fill(ds, "table");

            List<string> tableName = new List<string>();

            DataTable dt = ds.Tables[0];

            foreach (DataRow item in dt.Rows)

            {

                tableName.Add(item[0].ToString());

            }

3、SQL变量



 　　SqlCommand cmd = new SqlCommand(sql, sqlCon);

 　　SqlParameter para = new SqlParameter("@UHDATA", SqlDbType.Image);

 　　para.Value = UHDATA;　　　　//UHDATA 变量是 byte[]

 　　cmd.Parameters.Add(para);

 

 

1、更加数据库连接和sql语句获取字段值

        private string GetFieldStringValue(OleDbConnection oleconn, string ASqlStr)

        {

            string strResult = string.Empty;

            OleDbCommand comTemp = new OleDbCommand(ASqlStr);

            comTemp.Connection = oleconn;

            OleDbDataReader readerTemp = comTemp.ExecuteReader();

            if (readerTemp.HasRows)

            {

                readerTemp.Read();

                strResult = readerTemp.GetString(0);

            }

            readerTemp.Close();

            return strResult;

        }

 

 

参考：double数组转为image类型（即byte[]）

        public byte[] GetDoubleToByte(double[] d)

        {

            int size = Marshal.SizeOf(d[0]) * d.Length;

            IntPtr pnt = Marshal.AllocHGlobal(size);

            try

            {

                // Copy the array to unmanaged memory.

                Marshal.Copy(d, 0, pnt, d.Length);



                // Copy the unmanaged array back to another managed array.

                byte[] managedArray2 = new byte[d.Length * 8];



                Marshal.Copy(pnt, managedArray2, 0, d.Length * 8);

                return managedArray2;

            }

            finally

            {

                // Free the unmanaged memory.

                Marshal.FreeHGlobal(pnt);

            }

        }