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);
            }
        }