/// <summary>
/// 执行查询，并返回查询所返回结果集的第一行第一列。忽略额外的行或列
/// </summary>
/// <returns></returns>
public object ExecuteScalar()
{
PersistenceBroker broker = PersistenceBroker.Instance();
RelationalDatabase rdb = broker.GetDatabaseCopy(this.DatabaseName);
IDbCommand cmd = rdb.GetCommand();
cmd.CommandText = this.BuildForQuery(cmd);
DataTable dt = broker.ExecuteQuery(cmd, this.DatabaseName);
if (dt.Rows.Count == 0)
{
return(null);
}
else
{
return(dt.Rows[0][0]);
}
}
/// <summary>
/// 执行查询，并返回查询结果集
/// </summary>
/// <returns>查询结果</returns>
public DataTable Execute()
{
PersistenceBroker broker = PersistenceBroker.Instance();
RelationalDatabase rdb = broker.GetDatabaseCopy(this.DatabaseName);
IDbCommand cmd = rdb.GetCommand();
cmd.CommandText = this.BuildForQuery(cmd);
string cmdText = cmd.CommandText;
if (rdb.Vendor == DatabaseVendor.Oracle)
{
int topInd = cmdText.IndexOf("Top");
if (topInd != -1)
{
cmdText = cmdText.Substring(0, topInd) + cmdText.Substring(topInd + 6);
//使用ORCALE添加rownum的方法重装SQL语句
cmdText = PersistenceBroker.AddOracleTopWhere(cmdText, this.Top);
}
}
cmd.CommandText = cmdText;
return(broker.ExecuteQuery(cmd, this.DatabaseName));
}
