Scott Scott - 3 months ago 14
SQL Question

Parameterized ODBC Query works with VarChar but not DateTime?

As followup to this question, everything was working when I was manually defining the dates like

2016-05-01
as strings/varchars. However, when I went to convert to datetime I'm now getting empty results again. This is the code as it stands:

log("Connecting to SQL Server...");
string connectionString = "DSN=HSBUSTEST32;";

// Provide the query string with a parameter placeholder.
string queryString = "SELECT COUNT(*) FROM Table WHERE myDateTime >= ? AND myDateTime < ?";

// Specify the parameter value.
DateTime startDate = DateTime.Now;
DateTime endDate = startDate.AddHours(-1);

using (OdbcConnection connection = new OdbcConnection(connectionString))
{
// Create the Command and Parameter objects.
OdbcCommand command = new OdbcCommand(queryString, connection);
command.Parameters.Add("@startDate", OdbcType.DateTime).Value = startDate;
command.Parameters.Add("@endDate", OdbcType.DateTime).Value = endDate;

try
{
connection.Open();
OdbcDataReader reader = command.ExecuteReader();
while (reader.Read())
{
log(reader[0].ToString());
}
reader.Close();
}
catch (Exception ex)
{
log(ex.Message);
}
}


Again, if I were to replace the following:

DateTime startDate = DateTime.Now;
DateTime endDate = startDate.AddHours(-1);


with

string startDate = "2016-08-23";
string endDate = "2016-08-24";


And then change the
OdbcType
to
VarChar
everything works fine.

Answer

I believe your error is with the date range.

// Specify the parameter value.
DateTime startDate = DateTime.Now;
DateTime endDate = startDate.AddHours(-1);

endDate will be 1 hour less than start date. The comparison operator in your query is greater than first parameter and less than second parameter.

For example:

string queryString = "SELECT COUNT(*) FROM Table WHERE myDateTime >= '8/26/2016 14:30:00' AND myDateTime < '8/26/2016 13:30:00'";

No date exists that's greater than 2:30pm and less than 1:30pm of the same date. :)

Maybe you meant

DateTime startDate = DateTime.Now;
DateTime endDate = startDate.AddHours(1);
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