to solve sql exception Cannot find either column "partinfo" or the user-defined function or aggregate "partinfo.query", or the name is ambiguous - sql

Question

I use this pgm to get value from a column in xmlstring format named partinfo.which is one of the columns in table test.the partinfo column can be treated as another table containing many columns.and i want to read data from one of this column which is installed date in this case.but while executing i am getting a
sql exception: Cannot find either column "partinfo" or the user-defined
function or aggregate "partinfo.query", or the name is ambiguous.how
can i solve this.
namespace WpfApplication1
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public MainWindow()
{
InitializeComponent();
try {
SqlConnection con = new
SqlConnection("Data Source=NIP007\\SQLEXPRESS;
Initial Catalog=test;User ID=sa;Password=nest123#!");
con.Open();
string query = "SELECT [partinfo].query('.//InstalledDate').value('.','VARCHAR(MAX)')FROM [test]";
SqlCommand cmd = new SqlCommand(query, con);
// StringBuilder builder=new StringBuilder();
// string PartInfo=string.Empty;
SqlDataReader dr = cmd.ExecuteReader();
while (dr.Read())
{
string str5 =dr.ToString();
if (!string.IsNullOrEmpty(str5))
{
textBox1.Text=str5;
}
}
}
catch(Exception ex)
{
}
}
}
}

Answer 1

It is not clear what exactly where your error lies because, your SQL should work ok (Demo Here) and not return an error, although I am not sure the output is what you would want as it just concatenates all the installed dates in the XML as one long string:
As said in my previous answer if you have multiple Installed Dates per row, you will want to use CROSS APPLY TO get the installed dates as separate rows.
Demo SQL using CROSS APPLY
If you really want the dates concatenated to one string then I'd suggest using a string builder to do this:
try
{
string query = #"SELECT InstalledDate = x.value('InstalledDate[1]', 'DATETIME')
FROM dbo.Test
CROSS APPLY PartInfo.nodes('/DocumentElement/PartInfo') p (x);";
using (var con = new SqlConnection("Data Source=NIP007\\SQLEXPRESS;Initial Catalog=test;User ID=sa;Password=nest123#!"))
using (var cmd = new SqlCommand(query, con))
{
con.Open();
using (var dr = cmd.ExecuteReader())
{
var builder = new StringBuilder();
while (dr.Read())
{
string str5 = dr.GetString(0);
if (!string.IsNullOrEmpty(str5))
{
builder.Append(str5 + ",");
}
}
textBox1.Text = builder.ToString();
}
}
}
catch (Exception ex)
{
}
If this doesn't help can you post the DDL of your table Test and some sample data.
Thanks