Retrieve data from SQL put in variable

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I am trying this but in here i retrive 0 ..

What I have tried:

Public Function TotalYarnBalance_ByNtl_no(ByVal objModel) As Double

Dim sql As String = " select (isnull(sum(rec_frm_suppl_qty),0) +isnull(sum(ret_frm_knit_qty),0)+isnull(sum(ret_frm_subcont_qty),0)+isnull(sum(loan_frm_party),0))-((isnull(sum(iss_to_knitt_qty),0))+isnull(sum(iss_to_subcont_qty),0)+isnull(sum(ret_to_suppl_qty),0)+isnull(sum(loan_to_party),0)+sum(isnull(Sale,0))) as Balance from trans_yarn where ntl_no='" + objModel.ntl_order + "' and yarn_count='" + objModel.yarn_count + "' and yarn_type='" + objModel.yarn_type + "' and brand='" + objModel.brand + "' and lot_no ='" + objModel.lot_no + "' "

Dim dt_type As DataTable
Dim i As Double
dt_type = New DataTable("ViewYarnBalance")
da = New SqlDataAdapter(sql, conn)
conn.Open()
da.Fill(dt_type)
conn.Close()

Return i = dt_type.Rows(0)(0)

End Function

Posted 15-May-16 1:26am

turjoy

Updated 15-May-16 5:59am

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turjoy 15-May-16 10:41am

when this query execute datatable holds the value with single row..i want to return this value as a integer

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Sergey Alexandrovich Kryukov · Accepted Answer · 2016-05-15T05:59:00

Your approach is wrong from the very beginning. The query composed by concatenation with strings taken from UI. Not only repeated string concatenation is inefficient (because strings are immutable; do I have to explain why it makes repeated concatenation bad?), but there is way more important issue: it opens the doors to a well-known exploit called SQL injection.

This is how it works: http://xkcd.com/327.

Are you getting the idea? The string taken from a control can be anything, including… a fragment of SQL code.

What to do? Just read about this problem and the main remedy: parametrized statements: http://en.wikipedia.org/wiki/SQL_injection.

With ADO.NET, use this: http://msdn.microsoft.com/en-us/library/ff648339.aspx.

Please see my past answers for some more detail:
EROR IN UPATE in com.ExecuteNonQuery();,
hi name is not displaying in name?.

—SA

OriginalGriff · Accepted Answer · 2016-05-15T01:43:00

Firstly, stop doing it like that!
Do not concatenate strings to build a SQL command. It leaves you wide open to accidental or deliberate SQL Injection attack which can destroy your entire database. Use Parametrized queries instead:

VB

Using con As New SqlConnection(strConnect)
	con.Open()
	Using da As New SqlDataAdapter("SELECT MyColumn1, MyColumn2 FROM myTable WHERE mySearchColumn = @SEARCH", con)
		da.SelectCommand.Parameters.AddWithValue("@SEARCH", myTextBox.Text)
		Dim dt As New DataTable()
		da.Fill(dt)
		...
	End Using
End Using

Second, that is stuffed full of SUM operations, which will return null is there is any one null value in your column - so any single value of null will cause your sum to be zero.
Look at your data!

Retrieve data from SQL put in variable

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