我可以执行多条 SQL 语句吗？
当然可以！您可以在单个或多个SqlCommand 中执行它。 :)
UPDATE SQL 语句确实有效，表明电影已被拍摄，但
电影未添加到签出表中
您使用的是本地数据库吗？如果是，请查看Data not saving permanently to SQL table。
无论如何，我希望我的数据访问代码可以帮助您的开发。
免责声明：我知道使用SqlCommand 作为参数更好，但我很懒所以这里是string 版本。
public interface IDAL
{
void BeginTransaction();
void EndTransaction();
void SaveChanges();
DataTable RetrieveData(string query, [CallerMemberName] string callerMemberName = "");
string RetrieveString(string query, [CallerMemberName] string callerMemberName = "");
bool ExecuteNonQuery(string query, [CallerMemberName] string callerMemberName = "");
bool ExecuteNonQuery(string query, object[] parameters, [CallerMemberName] string callerMemberName = "");
}
public class MSSQLDAL : IDAL, IDisposable
{
private bool disposed = false;
private string _connectionString { get; set; }
private SqlTransaction _transaction { get; set; }
private SqlConnection _connection { get; set; }
private IsolationLevel _isolationLevel { get; set; }
private bool _isCommitted { get; set; }
public string ConnectionString
{
get { return _connectionString; }
}
public MSSQLDAL(string connectionString)
{
this.connectionString = _connectionString;
this._connection = new SqlConnection();
this._connection.ConnectionString = this._connectionString;
this._isolationLevel = IsolationLevel.ReadCommitted;
this._isCommitted = false;
}
public void BeginTransaction()
{
this.Open();
}
public void EndTransaction()
{
this.Close();
}
public void SaveChanges()
{
if(_transaction != null)
{
_transaction.Commit();
this._isCommitted = true;
}
this.EndTransaction();
}
public DataTable RetrieveData(string query, [CallerMemberName] string callerMemberName = "")
{
DataTable dataTable = new DataTable();
try
{
using (SqlCommand command = new SqlCommand())
{
command.Connection = _connection;
command.Transaction = _transaction;
command.CommandText = query;
command.CommandType = CommandType.Text;
using (SqlDataAdapter dataAdapter = new SqlDataAdapter(command))
{
dataAdapter.Fill(dataTable);
}
}
//this.AuditSQL(query, string.Empty);
}
catch (Exception ex)
{
this.AuditSQL(query, ex.Message, callerMemberName);
}
return dataTable;
}
public string RetrieveString(string query, [CallerMemberName] string callerMemberName = "")
{
string text = string.Empty;
try
{
using (SqlCommand oracleCommand = new SqlCommand())
{
oracleCommand.Connection = _connection;
oracleCommand.Transaction = _transaction;
oracleCommand.CommandText = query;
oracleCommand.CommandType = CommandType.Text;
using (SqlDataReader dataReader = oracleCommand.ExecuteReader())
{
dataReader.Read();
text = dataReader.GetValue(0).ToString();
}
}
//this.AuditSQL(query, string.Empty);
}
catch (Exception ex)
{
this.AuditSQL(query, ex.Message, callerMemberName);
}
return text;
}
public bool ExecuteNonQuery(string query, [CallerMemberName] string callerMemberName = "")
{
bool success = false;
try
{
using (SqlCommand command = new SqlCommand())
{
command.Connection = _connection;
command.Transaction = _transaction;
command.CommandText = query;
command.CommandType = CommandType.Text;
command.ExecuteNonQuery();
}
//this.AuditSQL(query, string.Empty);
success = true;
}
catch (Exception ex)
{
this.AuditSQL(query, ex.Message, callerMemberName);
success = false;
}
return success;
}
public bool ExecuteNonQuery(string query, object[] parameters, [CallerMemberName] string callerMemberName = "")
{
bool success = false;
try
{
using (SqlCommand command = new SqlCommand())
{
command.Connection = _connection;
command.Transaction = _transaction;
command.CommandText = query;
command.CommandType = CommandType.Text;
command.Parameters.AddRange(parameters);
command.ExecuteNonQuery();
}
//this.AuditSQL(query, string.Empty);
success = true;
}
catch (Exception ex)
{
this.AuditSQL(query, ex.Message, callerMemberName);
success = false;
}
return success;
}
private void Open()
{
if(_connection.State == ConnectionState.Closed)
{
_connection.Open();
_transaction = _connection.BeginTransaction(_isolationLevel);
}
}
private void Close()
{
if (!this._isCommitted)
{
if (this._transaction != null)
{
this._transaction.Rollback();
}
}
if(this._connection.State == ConnectionState.Open)
{
this._connection.Close();
}
}
private void AuditSQL(string query, string message, string callerMemberName = "")
{
StringBuilder stringBuilder = new StringBuilder();
stringBuilder.AppendLine("**************************************************************************************************");
stringBuilder.AppendLine(string.Format("DATETIME: {0}", DateTime.Now.ToString("MM/dd/yyyy HHmmss")));
stringBuilder.AppendLine(string.Format("SQL: {0}", query));
stringBuilder.AppendLine(string.Format("MESSAGE: {0}", message));
if (!string.IsNullOrWhiteSpace(callerMemberName))
{
stringBuilder.AppendLine(string.Format("METHOD: {0}", callerMemberName));
}
stringBuilder.AppendLine("**************************************************************************************************");
Logger.WriteLineSQL(stringBuilder.ToString()); // Log the query result. Add an #if DEBUG so that live version will no longer log.
}
public void Dispose()
{
Dispose(true);
GC.SuppressFinalize(this);
}
protected virtual void Dispose(bool disposing)
{
if (!disposed)
{
if (disposing)
{
if (!this._isCommitted)
{
if (this._transaction != null)
{
this._transaction.Rollback();
}
}
this._transaction.Dispose();
this._connection.Dispose();
}
// Free your own state (unmanaged objects).
// Set large fields to null.
// Free other state (managed objects).
this._transaction = null;
this._connection = null;
disposed = true;
}
}
}
示例用法：
public void CheckOut(object sender, EventArgs e)
{
string connectionString = ConfigurationManager.ConnectionStrings["DefaultConnection"].ConnectionString; // Assuming it is in your web.config
try
{
using(MSSQLDAL dal = new MSSQLDAL(connectionString))
{
dal.BeginTransaction();
string updateQuery = "UPDATE Content SET DateChecked=@DateChecked, CheckedOut=@CheckedOut WHERE MovieID=@MovieID";
SqlParameter uDateChecked = new SqlParameter("DateChecked", SqlDbType.DateTime);
uDateChecked = DateTime.Now;
SqlParameter uCheckedOut = new SqlParameter("CheckedOut", SqlDbType.VarChar);
uCheckedOut = 'Y';
SqlParameter uMovieID = new SqlParameter("MovieID", SqlDbType.Int);
uMovieID = CheckOutList.SelectedValue;
ICollection<SqlParameter> updateParameters = new List<SqlParameter>();
updateParameters.Add(uDateChecked);
updateParameters.Add(uCheckedOut);
updateParameters.Add(uMovieID);
bool updateSuccessful = dal.ExecuteNonQuery(updateQuery, updateParameters.ToArray());
string insertQuery = "INSERT INTO checkout (MovieID, SubscriberID) VALUES (@MovieID, @SubscriberID)";
SqlParameter iSubscriberID = new SqlParameter("SubscriberID", SqlDbType.VarChar);
iSubscriberID = loginName.Text;
SqlParameter iMovieID = new SqlParameter("MovieID", SqlDbType.Int);
iMovieID = CheckOutList.SelectedValue;
ICollection<SqlParameter> insertParameters = new List<SqlParameter>();
insertParameters.Add(iSubscriberID);
insertParameters.Add(iMovieID);
bool insertSuccessful = dal.ExecuteNonQuery(insertQuery, insertParameters.ToArray());
if(updateSuccessful && insertSuccessful)
{
dal.SaveChanges();
lblInfo.Text = "Movie Checked Out";
}
else
{
lblInfo.Text = "Something is wrong with your query!";
}
}
}
catch(Exception ex)
{
StringBuilder sb = new StringBuilder();
sb.AppendLine("Error reading the database.");
sb.AppendLine(ex.Message);
if(ex.InnerException != null)
sb.AppendLine(ex.InnerException.Message);
lblInfo.Text = sb.ToString();
}
}
如何在一个命令中执行多个 SQL 语句？
您只需使用BEGIN 和END; 封装您的查询。
例如：
BEGIN
SELECT 'A';
SELECT * FROM TableA;
END;
请注意，您需要在语句后加上;。如果我是你，我会使用StringBuilder 来写我的长查询。此外，仅当您不读取任何数据时，将多个查询作为一个发送才有用。
IDAL 接口有什么用？
在我的一些项目中，我不得不使用不同的数据库。使用相同的接口，我能够为 Oracle、MSSql 和 MySql 创建一个 DAL 类，而代码更改非常少。这也是OOP方式。 :)