Develop Reference

sql query to show data from price between two columns C#

EDIT: I am not able to format my code below, if any one can fix it.
I am new to sql queries and still learning.
Table Name: CommissionSetupTable.
I want to display #Paisa if gross_amount is between the range of #FromRate and #ToRate
Below is my code:
string paisa;
private void load_commission_setup()
{
SqlCeConnection conn = null;
SqlCeCommand cmd = null;
SqlCeDataReader rdr = null;
try
{
conn =
new SqlCeConnection(
#"Data Source=|DataDirectory|\Database.sdf;Persist Security Info=False");
conn.Open();
int rowindex = purchaseBillTableDataGridView.Rows.Count - 1;
gross_amount = double.Parse(purchaseBillTableDataGridView[10, rowindex].Value.ToString());
// Gross Amount is between the ranges of FromRate and ToRate.
cmd = new SqlCeCommand("SELECT Paisa FROM CommissionSetupTable WHERE='" + gross_amount.ToString() + "' BETWEEN #FromRate AND #ToRate;", conn);
rdr = cmd.ExecuteReader();
if (rdr == null)
{
}
else
{
while (rdr.Read())
{
paisa = rdr["Paisa"].ToString();
}
rdr.Close();
cmd.Dispose();
}
}
finally
{
conn.Close();
int rowindex = purchaseBillTableDataGridView.Rows.Count - 1;
purchaseBillTableDataGridView[11, rowindex].Value = paisa;
}
}

The correct syntax to use here is the following
cmd = new SqlCeCommand(#"SELECT Paisa FROM CommissionSetupTable
WHERE #gross BETWEEN FromRate AND ToRate;", conn);
Notice that the two field names should not be prefixed with #, otherwise they will be considered parameters placeholders.
And now, before executing the command, add the parameter for the #gross placeholder
cmd.Parameters.Add("#gross", SqlDbType.Decimal).Value = gross_amount;
I don't know what is the exact datatype of the columns FromRate and EndRate, but
note that you should use the correct datatype for your parameter. Do not pass a string and expect the database engine do the conversion for you. (or worse concatenate your value to the rest of the sql using ToString()). This is always wrong also if sometime the database engine could understand your values.
EDIT
Also, following your comments below, it appears that this line is wrong
int rowindex = purchaseBillTableDataGridView.Rows.Count - 1;
If your DataGridView has the property AllowUserToAddRow set to True then you want to use
int rowindex = purchaseBillTableDataGridView.Rows.Count - 2;
because the first line points to the empty row added to the DataGridView for inserting a new record.

Conversion failed when converting the nvarchar value to data type int

I am getting the error of conversion failed in my codebehind. My code is below:
using (SqlCommand cmd = new SqlCommand((tempUsertype == "0" ? "Select * from tbl_students" : "Select * from tbl_students where Id in (Select Id from tbl_students where NgoId=#NgoId)"), conn))
{
cmd.Parameters.AddWithValue("#NgoId", Convert.ToString(Session["User"]));
SqlDataAdapter da = new SqlDataAdapter(cmd);
DataSet ds = new DataSet();
da.Fill(ds);
ddlStudent.DataValueField = ds.Tables[0].Columns["Id"].ToString();
ddlStudent.DataTextField = ds.Tables[0].Columns["first_name"].ToString();
ddlStudent.DataSource = ds.Tables[0];
ddlStudent.SelectedIndex = 0;
if (Session["UserType"] == "1" || Session["UserType"] == "2")
{
ddlStudent.Enabled = false;
}
else
{
ddlStudent.Items.Insert(0, new ListItem() { Text = "--Select NGO--", Value = "0" });
ddlStudent.Enabled = true;
}
}
I'm getting following error:
Conversion failed when converting the nvarchar value to data type int.
What changes has to be done here?

I guess that NgoId is an int but you're assigning a string. So this might fix it:
var p = new SqlParameter("#NgoId", SqlDbType.int).Value = int.Parse(Convert.ToString(Session["User"]));
cmd.Parameters.Add(p);
Edit: since you have commented that the session stores the username but the NgoId is an int-column you have three options:
change the session to store the user-id int instead of the name
change the column to store the username
select the user-id from the table where the username is stored.
I would either prefer the first or the last option.
This works if you also prefer the last approach:
string sql = "Select * from tbl_students";
if(tempUsertype != "0")
{
sql = #"Select s.*
from tbl_students s
where s.NgoId in (Select u.NgoId
from tbl_User u
where u.username = #Username)";
}
using (var cmd = new SqlCommand(sql, conn))
{
var p = new SqlParameter("#Username", SqlDbType.varchar);
p.Value = Convert.ToString(Session["User"]);
cmd.Parameters.Add(p);
// ...
}

Try this:
cmd.Parameters.Add("#NgoId", SqlDbType.Int).Value = Convert.ToString(Session["User"]);
This will coerce the NgoId parameter to the SQL Server int data type.

How can I get the result of a stored procedure in C#?

Here is my code in C#:
float r_discountValue = 0;
SqlConnection con = Constant.GetConnection();
SqlCommand cmd = new SqlCommand("Coupon_GetDiscountFromValidCouponCode", con);
cmd.CommandType = CommandType.StoredProcedure;
cmd.Parameters.Add("#PKCouponCode", SqlDbType.VarChar);
cmd.Parameters["#PKCouponCode"].Value = "DIS_77";
try
{
con.Open();
SqlDataReader reader = cmd.ExecuteReader();
if(reader.Read()){
r_discountValue = float.Parse(reader[0].ToString());
}
reader.Close();
}
catch(Exception exception)
{
throw exception;
}
finally{
con.Close();
}
return r_discountValue;
The stored procedure:
ALTER PROCEDURE [dbo].[Coupon_GetDiscountFromValidCouponCode]
#PKCouponCode varchar(50)
AS
SELECT *
FROM Coupon
WHERE CouponCode = #PKCouponCode AND Valid = 1
Here is how the DB looks like:
I encounter an error
Input string was not in a correct format
I don't know what's thing is going wrong, any ideas?

If you want the discount value, then you should return only the discount from the SP (since it is named GetDiscountfrom...)
SELECT CouponDiscount FROM Coupon WHERE CouponCode = #PKCouponCode AND Valid = 1
This will make it a one-column resultset, which matches the access reader[0] from C#.
The other option is of course to change the C# side to read the second item (index 1) or reference the column by name, e.g.
r_discountValue = float.Parse(reader[1].ToString());
r_discountValue = float.Parse(reader["CouponDiscount"].ToString());
You would have got Input string was not in a correct format. because it was reading "DIS_77" which float.parse cannot process.

You are using first column i.e.CouponCode for fetching discount. instead of that you need to use second column ie. couponDiscount
So try something like this
r_discountValue = float.Parse(reader["CouponDiscount"].ToString());

Return an sql variable's value from within an Oracle Sql Query back to .NET code

For the past few hours I am trying to do the simplest of the simple things (at least for SQL SERVER) in an Oracle Data Base, through a .NET application using ADO.NET. It seems impossible.
For SQL SERVER I would do this simple task, supposing I have an SqlCommand object
comm.CommandText = #"
DECLARE #next_id INT
SET #next_id = (SELECT ISNULL(MAX(id_col),0) FROM TABLE_1) + 1
INSERT INTO TABLE_1 (id_col, col1, ...) VALUES (#next_id, val1, ...)
SELECT #next_id";
int id = Convert.ToInt32(comm.ExecuteScalar());
That would insert a new record to table TABLE_1 and I would take back the new id in the "id" variable in c# code.
Four simple steps
Declare a variable
Set it to the next available id
Insert the record with the new variable
Return the variable's value
Ok I managed to declare the variable in Oracle query. Also I (think) I managed to give it a value (With SELECT INTO)
How can I get back this variable's value back in c#? How can i SELECT a variable's value to the output stream in Oracle SQL?
I know that there are better ways to achieve getting back an identity column, but that's not the question here. It could be a totally different example. The question is simple.: I have declared a variable inside an oracle sql script that will be executed from within .net app. How can i get the variable's value back to c#, from an oracle query? What is the above code's equivalent with Oracle ADO.NET query?

You'll want to use ODP.NET (Oracle's Oracle Data Access Components):
An example of this is below. Note that in ODP.NET, you can establish a parameters direction (input, inputoutput, output, returnvalue) to correspond with the parameters of the procedure or statement you're running. In this example, I'm grabbing a returnvalue, which is an ID that is generated by the db via a sequence and trigger (its created automagically as far as the .NET app is concerned):
int event_id = 0;
using (OracleConnection oraConn = new OracleConnection(connStr))
{
string cmdText = #"insert into EVENT
(EVENT_NAME, EVENT_DESC)
values
(:EVENT_NAME, :EVENT_DESC)
RETURNING EVENT_ID INTO :EVENT_ID
";
using (OracleCommand cmd = new OracleCommand(cmdText, oraConn))
{
oraConn.Open();
OracleTransaction trans = oraConn.BeginTransaction();
try
{
OracleParameter prm = new OracleParameter();
cmd.BindByName = true;
prm = new OracleParameter("EVENT_NAME", OracleDbType.Varchar2);
prm.Value = "SOME NAME"; cmd.Parameters.Add(prm);
prm = new OracleParameter("EVENT_DESC", OracleDbType.Varchar2);
prm.Value = "SOME DESC"; cmd.Parameters.Add(prm);
prm = new OracleParameter( "EVENT_ID"
, OracleDbType.Int32
, ParameterDirection.ReturnValue);
cmd.Parameters.Add(prm);
cmd.ExecuteNonQuery();
trans.Commit();
// return value
event_id = ConvertFromDB<int>(cmd.Parameters["EVENT_ID"].Value);
}
catch
{
trans.Rollback();
throw;
}
finally
{
trans.Dispose();
}
oraConn.Close();
}
}
The ConvertFromDB is just a generic to cast the return value to its .NET equivalent (an int in this case).
Hope that helps.
EDIT:
You can easily bind an array of values (and retrieve an array of return values) in ODP.NET:
using (OracleConnection oraConn = new OracleConnection(connStr))
{
string cmdText = #"insert into TEST_EVENT
(EVENT_NAME, EVENT_DESC)
values
(:EVENT_NAME, :EVENT_DESC)
RETURNING EVENT_ID INTO :EVENT_ID
";
using (OracleCommand cmd = new OracleCommand(cmdText, oraConn))
{
oraConn.Open();
OracleTransaction trans = oraConn.BeginTransaction();
try
{
string[] event_names = new string[2];
string[] event_descs = new string[2];
int[] event_ids = new int[2];
event_names[0] = "Event1";
event_descs[0] = "Desc1";
event_names[1] = "Event2";
event_descs[1] = "Desc2";
OracleParameter prm = new OracleParameter();
cmd.Parameters.Clear();
cmd.ArrayBindCount = 2;
cmd.BindByName = true;
prm = new OracleParameter("EVENT_NAME", OracleDbType.Varchar2);
prm.Value = event_names; cmd.Parameters.Add(prm);
prm = new OracleParameter("EVENT_DESC", OracleDbType.Varchar2);
prm.Value = event_descs; cmd.Parameters.Add(prm);
prm = new OracleParameter( "EVENT_ID"
, OracleDbType.Int32
, ParameterDirection.ReturnValue);
cmd.Parameters.Add(prm);
cmd.ExecuteNonQuery();
trans.Commit();
// get return values
event_ids = (int[])(cmd.Parameters["EVENT_ID"].Value);
}
catch
{
trans.Rollback();
throw;
}
finally
{
trans.Dispose();
}
oraConn.Close();
}
}

C# and PostgreSQL

Can anyone show me a working example of using a cursor returned from PLSQL to C# code?
I found many examples showing how to fill a dataSet with returned data, but I cannot find how to use that cursor with a DataReader, so as a result I have {unnamed portal}.
NpgsqlTransaction tr = (NpgsqlTransaction) Connection.BeginTransaction();
NpgsqlCommand cursCmd = new NpgsqlCommand("someStoredProcedure(:inRadius)", (NpgsqlConnection) Connection);
cursCmd.Transaction = tr;
NpgsqlParameter rf = new NpgsqlParameter("ref", NpgsqlTypes.NpgsqlDbType.Refcursor);
rf.Direction = ParameterDirection.InputOutput;
cursCmd.Parameters.Add(rf);
I have to add this to use NpgsqlDataReader myReader; correctly:
tr.Commit();
When I wrote fetch after the sql command, it works but it is not suitable.

For your reference:
/// <summary>
/// Get data from the returning refcursor of postgresql function
/// </summary>
/// <param name="FunctionName">Function name of postgresql</param>
/// <param name="Parameters">parameters to pass to the postgresql function</param>
/// <param name="ErrorOccured">out bool parameter to check if it occured error</param>
/// <returns></returns>
public List<DataTable> GetRefCursorData(string FunctionName, List<object> Parameters, out bool ErrorOccured)
{
string connectstring = ""; //your connectstring here
List<DataTable > dtRtn =new List<DataTable>();
NpgsqlConnection connection = null;
NpgsqlTransaction transaction = null;
NpgsqlCommand command = null;
try
{
connection = new NpgsqlConnection(connectstring);
transaction = connection.BeginTransaction();
command = new NpgsqlCommand();
command.Connection = connection;
command.CommandType = CommandType.StoredProcedure;
command.CommandText = FunctionName;
command.Transaction = transaction;
//
if (Parameters != null)
{
foreach (object item in Parameters)
{
NpgsqlParameter parameter = new NpgsqlParameter();
parameter.Direction = ParameterDirection.Input;
parameter.Value = item;
command.Parameters.Add(parameter);
}
}
//
NpgsqlDataReader dr = command.ExecuteReader();
while (dr.Read())
{
DataTable dt = new DataTable();
command = new NpgsqlCommand("FETCH ALL IN " + "\"" + dr[0].ToString() + "\"", Connection); //use plpgsql fetch command to get data back
NpgsqlDataAdapter da = new NpgsqlDataAdapter(command);
da.Fill(dt);
dtRtn.Add(dt); //all the data will save in the List<DataTable> ,no matter the connection is closed or returned multiple refcursors
}
ErrorOccured = false;
transaction.Commit();
}
catch
{
//error handling ...
ErrorOccured = true;
if (transaction != null) transaction.Rollback();
}
finally
{
if (connection != null) connection.Close();
}
return dtRtn;
}

I have got some answers on my question.
Problem: I have a stored PLSQL procedure which returns refCursor. I have to get the returned data with a DataReader, but wwhen I added parameters, the db returned <unnamed portal>.
To walk through all returned data I have to write my code like so:
NpgsqlTransaction tr = (NpgsqlTransaction) Connection.BeginTransaction();
NpgsqlCommand cursCmd = new NpgsqlCommand("someStoredProcedure", (NpgsqlConnection) Connection);
cursCmd.Transaction = tr;
NpgsqlParameter rf = new NpgsqlParameter("ref", NpgsqlTypes.NpgsqlDbType.Refcursor);
rf.Direction = ParameterDirection.InputOutput;
cursCmd.Parameters.Add(rf);
NpgsqlParameter param2 = new NpgsqlParameter("param1", NpgsqlTypes.Int32);
rf.Direction = ParameterDirection.Input;
cursCmd.Parameters.Add(param2);
NpgsqlDataReader r = cmd.ExecuteReader();
while (r.Read())
{
; // r.GetValue(0);
}
r.NextResult();
while(r.Read())
{
;
}
tr.Commit();
Notice that you don't write your parameters in sql like func(:param1).
If you have parameters in your function, assign only the function name to the CommandText property and add parameters to the NpgsqlCommand.Parameters collection as usual. Npgsql will take care of binding your parameters correctly.
But now I have another problem. When I pass another output parameter to my CommandText, I have two fields in my result. One of them is 0{my first output param} and the other is <unnamed portal>.
In Oracle, I can directly convert a RefCursor parameter to a DataReader, but in postgresql, I cannot.

First of all, here is some documentation that could be useful: Npgsql doc
In this documentation you'll find a NpgsqlDataAdapter. This object also has a Fill() method (inherited from DbDataAdapter). This method can take a DataSet and a cursor. It will fill the DataSet with the data returned by your cursor.
You can't actually give a DataReader to this method, but you can give a DataTable, I think you can manage to do something with this.

I have solved the problem with Out parameters by using two commands in the same transaction.
In the first command, I read the out parameter and then execute the next command.
The second command looks like:
var cmd2 = new NpgsqlCommand("FETCH ALL FROM \"list\"", (NpgsqlConnection) Connection)
Where list the name of cursor created inside the stored procedure. As a result I get data selected from the db.