Question

我正在尝试将两个SQL查询结果绑定到一个DataTable，以便我可以将DataTable设置为图表的数据源，但我不确定如何去做。我似乎无法将SQL查询结果添加到我需要的DataTable中的特定列。

这是我的代码：

// retrieve connection from configuration settings 
connection = new SqlConnection(RoleEnvironment.GetConfigurationSettingValue("DataConnectionString").ToString());

// Calling SQL query 
SqlCommand commandGraph = new SqlCommand("SELECT AtmosphericPressure FROM Buoy3v3 WHERE time > '" + TextBox1_fromDate.Text + "' AND time < '" + TextBox2_toDate.Text + "';", connection);
commandGraph.CommandType = CommandType.Text;

SqlCommand commandGraph1month = new SqlCommand("SELECT AtmosphericPressure AS apMonth FROM Buoy3v3 WHERE time > (DATEADD(month, 1,'" + TextBox1_fromDate.Text + "')) AND time < (DATEADD(month, 1,'" + TextBox2_toDate.Text + "')) ;", connection);
commandGraph1month.CommandType = CommandType.Text;

//connection open
connection.Open();

DataTable dt = new DataTable();
dt.Columns.Add("AP");
dt.Columns.Add("AP1month");


using (SqlDataReader reader = commandGraph.ExecuteReader())
{

dt.Load(reader);
}

using (SqlDataReader reader1 = commandGraph1month.ExecuteReader())
{
   dt.Load(reader1);
}

Chart1.DataSource = dt;

Chart1.Series["Series1"].YValueMembers = "AP";
Chart1.Series["Series1"].YValueMembers = "AP1month";

//connection close
connection.Close();

Answer 1

仅使用一个查询。这样的事情可以奏效：

SELECT t1.AtmosphericPressure, t2.AtmosphericPressure
FROM Buoy3v3 t1
LEFT JOIN Buoy3v3 t2 ON t1.time = (DATEADD(month, 1,t2.time))
WHERE ...

这应该导致2条线并排运行 - 结果可能看起来像这样：

1 |  ..xxxxx    xxxxxxx
2 |   x.... x  x ......
3 |  x     . xx..
4 |         ...             
5 |_______________________
     1   2   3   4   5

在您的代码中，您只有一列AtmosphericPressure。如果你真的想使用2个查询，你可以让它们返回2列 -

SELECT AtmosphericPressure, null FROM Buoy3v3
SELECT null, AtmosphericPressure FROM Buoy3v3

这应该导致两行，但第二行将从第一次结束开始

此外，您的代码容易受到SQL注入攻击，请考虑使用参数化查询 - 例如commandGraph.Parameters.Add()

将2个SQL查询绑定到一个数据表中

1 个答案: