关于sql：我想在进行多次选择和联合C#之后从数据集中检索数据

I would like to retrieve data from dataset after multi select and union C#

我想从数据集中检索数据(Visual Studio 2010)
这是sql语句：

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SELECT NO_IDENT_1
FROM P240538
WHERE (P240538.DATE_dt > {2011/04/24})
Union
SELECT NO_IDENT_2
FROM P240538
WHERE (P240538.DATE_dt > {2011/04/24})

如果我不使用union一次执行一条语句，它将起作用。

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string sqltring ="SELECT NO_IDENT_1 FROM P240538 WHERE (P240538.DATE_dt > {2011/04/24}) Union SELECT NO_IDENT_2 FROM P240538 WHERE (P240538.DATE_dt > {2011/04/24})"

OleDbConnection ConnFoxPro = new OleDbConnection(Properties.Settings.Default.S_ConnFoxPro26);
try
{
ConnFoxPro.Open();
// MessageBox.Show(" Connection State =" + ConnFoxPro.State);
}
catch (OleDbException ex)
{
string errorMessages ="";
for (int i = 0; i < ex.Errors.Count; i++)
{
errorMessages +="Index #" + i +"\
" +
"Message:" + ex.Errors[i].Message +"\
" +
"NativeError:" + ex.Errors[i].NativeError +"\
" +
"Source:" + ex.Errors[i].Source +"\
" +
"SQLState:" + ex.Errors[i].SQLState +"\
";
}
System.Diagnostics.EventLog log = new System.Diagnostics.EventLog();
log.Source ="Mon application";
log.WriteEntry(errorMessages);
Console.WriteLine("Vous avez un exeption. Svp Contacter votre administrateur de system cdd");
}
{

try
{
//MessageBox.Show(RqCompte);
OleDbDataAdapter DA_ID = new OleDbDataAdapter(sqltring, ConnFoxPro);
DataSet Ds_ID = new DataSet();
DA_ID.Fill(Ds_ID,"P240538");

foreach (DataTable thisTable in Ds_ID.Tables)
{
// For each row, print the values of each column.

foreach (DataRow row in thisTable.Rows)
{
// string rowdata = row.ItemArray[0].ToString().Replace("","");
string rowdata1 = row["NO_IDENT_1"].ToString().Replace("","");
if (rowdata1 !="")
liste_No_Ident += rowdata1 +"";// +"NOMBRE =" + row["nbr_doublon"] +"\
\
";
string rowdata2 = row["NO_IDENT_2"].ToString().Replace("","");
if (rowdata2 !="")
liste_No_Ident += rowdata2 +"";// +"NOMBRE =" + row["nbr_doublon"] +"\
\
";

}
}
}
catch (Exception e)
{
}