how to select max value from database in vb.net - vb.net

i have database with different value
number_reg
10
9
15
18
I tried
sql = "SELECT * from table where number_reg=(SELECT max(number_reg)from table)"
cmd = New OdbcCommand(sql, conn)
dtreader = cmd.ExecuteReader
If dtreader.Read Then
textbox1.Text = dtreader.Item("number_reg")
Else
textbox1.Text = "0"
End If
but the output is 10 how to get output is 18 ??

Related

error as index was outside the bounds of the array?

I tried debugging the code...but couldnt rectify...Hope someone gives suggestions
index was outside the bounds of the array
Private Sub loaditems()
Try
sqL = "SELECT bills.productname,bills.qty,bills.unitprice,bills.totalamt FROM bills INNER JOIN transactionDetails ON bills.invoiceno = transactionDetails.invoiceID where bills.invoiceno ='" & Trim(lblInvoice.Text) & " '"
ConnDB()
cmd = New SqlCommand(sqL, conn)
dr = cmd.ExecuteReader(CommandBehavior.CloseConnection)
dgw.Rows.Clear()
Do While dr.Read = True
dgw.Rows.Add(dr(1), dr(0), dr(2), dr(3))
lblbalance.Text = dr(4)
dgw.Height += 19
x += 19
Loop
MsgBox("data showing")
Y = x - 30
dgw.Height = dgw.Height - 20
change.Location = New Point(49, 280 + Y)
lblbalance.Location = New Point(249, 280 + Y)
lblLine.Location = New Point(52, 299 + Y)
lblOR.Location = New Point(86, 315 + Y)
lblThank.Location = New Point(106, 331 + Y)
btnexit.Location = New Point(198, 369 + Y)
btnprint.Location = New Point(104, 369 + Y)
Panel1.Height = Panel1.Height + Y
Me.Height = Me.Height + Y
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
The index starts counting at 0.
this means that:
column 1 has a index of 0
column 2 has a index of 1.
column 3 has a index of 2.
column 4 has a index of 3.
Column 5 has a index of 4. <- dr(4) references column 5.
column 6 has a index of 5
dr(4) references to the fifth column, which does not exist. it only has 4 columns.

Display number of rows and columns

I have in my table MS Access named ( Table1 ) two fields ( ID1 - Team1 ).
With NumericUpDown1 i select the number of rows that i want to display after randomize in DataGridView2.With NumericUpDown2 i select the number of columns that i want to display after randomize in DataGridView2.If i choose with NumericUpDown2 only one column ( the number 1 ) it work very well with this query :
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Con_randomize()
Dim rows As Integer
If Not Integer.TryParse(NumericUpDown1.Value, rows) Then
MsgBox("NUMBER NOT AVAILABLE", MsgBoxStyle.Critical + MsgBoxStyle.OkOnly, "Error")
NumericUpDown1.Value = ""
NumericUpDown1.Focus()
Exit Sub
End If
If NumericUpDown2.Value = 1 Then
Dim sql As String = String.Format("SELECT Top {0} ID1,Team1 From Table1 ORDER BY RND(-(100000*ID1)*Time())", rows)
InfoCommand = New OleDbCommand(sql, Con_randomize)
InfoAdapter = New OleDbDataAdapter()
InfoAdapter.SelectCommand = InfoCommand
InfoTable = New DataTable()
InfoAdapter.Fill(InfoTable)
DataGridView2.DataSource = InfoTable
DataGridView2.Columns(0).HeaderText = "NUMERO"
DataGridView2.Columns(1).HeaderText = "CATEGORY1"
End If
End Sub
How to make if i choose with NumericUpDown2 the number 2 or 3 columns i want to display in Datagridview2.
The columns will be named ( CATEGORY2 - CATEGORY3 ) . for example ( 1 Victor - David - Vincent ) ( 2 wiliam- George - Joseph ) ..in my only field named Team1 I have a hundred of the names
I'm not 100% sure why you need a query to initialize the data, but give this a go. It will automatically create the columns the way you need them.
' If NumericUpDown2.Value = 1 Then ' Comment This If Block Out
' Create the Teams String
Dim teamsString as New System.Text.StringBuilder("")
For i as Integer = 1 to Convert.ToInt32(NumericUpDown2.Value)
teamsString.Append(", (SELECT Top 1 Team1 From Table1 ORDER BY RND(-(100000*ID1)*Time())) as Category" + i.ToString())
Next
Dim sql As String = String.Format("SELECT Top {0} ID1" + teamsString.ToString() + " From Table1 ORDER BY RND(-(100000*ID1)*Time())", rows)
InfoCommand = New OleDbCommand(sql, Con_randomize)
InfoAdapter = New OleDbDataAdapter()
InfoAdapter.SelectCommand = InfoCommand
InfoTable = New DataTable()
InfoAdapter.Fill(InfoTable)
DataGridView2.DataSource = InfoTable
DataGridView2.Columns(0).HeaderText = "NUMERO"
' Don't Need This, We Made It the Binding Name
' DataGridView2.Columns(1).HeaderText = "CATEGORY1"

how to convert database table values to array string?

I want to read the values from the database and convert it to a string array.
strQ = "SELECT * FROM Courses"
cmd = New SqlCommand(strQ, conn)
da = New SqlDataAdapter(cmd)
ds = New DataSet
da.Fill(ds, "Courses")
Dim i As Integer = 0
Dim j As Integer = 0
For i = 0 To ds.Tables(0).Columns.Count - 1
Me.ListView1.Columns.Add(ds.Tables(0).Columns(i).ColumnName.ToString())
Next
For i = 0 To ds.Tables(0).Rows.Count - 1
For j = 0 To ds.Tables(0).Columns.Count - 1
itemcol(j) = ds.Tables(0).Rows(i)(j).ToString()
Next
Dim lvi As New ListViewItem(itemcol)
Me.ListView1.Items.Add(lvi)
Next
I want to convert it to array format.
Edit from comments: Basically we're are dealing with courses and the number of students. The numbers are the student IDs who are taking the course. Here's some sample data:
jb(0) = {1,2,3,4,5} 'CIT121
jb(1) = {1,2,6,7,8} 'CIT141
jb(2) = {6,7,8,15,16} 'CIT202
jb(3) = {4,10,11} 'CIT203
You can use mentioned code
For i = 0 To ds.Tables(0).Columns.Count - 1
ds.Tables(0).Rows(i).ItemArray.[Select](Function(x) x.ToString()).ToArray()
Next

use select case condition with SQL query statement in vb.net

I try to use select case statement with SQL statement
I have 4 columns when the lbl1.text equal 1 then x = "column1" and put this value in the SQL statement
when I try this code
Dim x As String
Select Case lbl1.Text
Case 1
x = "column1"
Case 2
x = " column2"
Case 3
x = " column3"
Case 4
x = " column4"
DGV1.Columns.Clear()
Dim dt As New DataTable
dt.Clear()
DGV1.Visible = True
Dim comm2 As New SqlCommand
comm2.CommandText = Nothing
DGV1.Refresh()
comm2.CommandText = "select first_name,last_name,age from students where " + x + "=" + "yes" + ""
comm2.Connection = sqlconn
sqlconn.Open()
dr2 = comm2.ExecuteReader
dt.Load(dr2)
DGV1.AutoGenerateColumns = True
DGV1.DataSource = dt
DGV1.Refresh()
sqlconn.Close()
DGV1.Visible = True
comm2.Dispose()
End Select
and when lbl1.text = 1 or 2 or 3 it doesn't run the SQL statement but when the lbl1.text = 4 it's run SQL statement
can any one help me in this code
try this code, i just don't know if the break is the right syntax, but i guarantee you that this is the right code
` Dim x As String
Select Case lbl1.Text
Case 1
x = "column1"
Case 2
x = " column2"
Case 3
x = " column3"
Case 4
x = " column4"
End Select
DGV1.Columns.Clear()
Dim dt As New DataTable
dt.Clear()
DGV1.Visible = True
Dim comm2 As New SqlCommand
comm2.CommandText = Nothing
DGV1.Refresh()
comm2.CommandText = "select first_name,last_name,age from students where " + x + "=" + "yes" + ""
comm2.Connection = sqlconn
sqlconn.Open()
dr2 = comm2.ExecuteReader
dt.Load(dr2)
DGV1.AutoGenerateColumns = True
DGV1.DataSource = dt
DGV1.Refresh()
sqlconn.Close()
DGV1.Visible = True
comm2.Dispose()`

Transactions in vb.net locks table and SELECT gets timeout

I have the following problem:
Inside one sqltransaction in vb.net I INSERT data into several tables.
it is something like this:
...
sqltransaction = connection.begintransaction
INSERT into table1
...
for i=1 to x
...
INSERT into table2
...
SELECT FROM table3
...
INSERT into table3
...
next i
sqltransaction.commit
...
Private Sub salveazaCerereaDeOferta()
If checkCompletion() = 1 Then
Dim conn As New SqlConnection(My.Settings.GestiuneService2012_beSQLConnectionString)
conn.Open()
Dim sqlTrans As SqlTransaction = conn.BeginTransaction()
Try
Dim cmdInsertCerereOferta As SqlCommand = conn.CreateCommand
cmdInsertCerereOferta.Transaction = sqlTrans
cmdInsertCerereOferta.CommandText = "INSERT INTO ListaCereriOferte (IDFurnizor,NrCerereOferta,DataCerereOferta,IDModTransCerereOferta,ObservatiiCerereOferta)" + _
" VALUES (#IDFurnizor,#NrCerereOferta,#DataCerereOferta,#IDModTransCerereOferta,#ObservatiiCerereOferta);" + _
" SELECT SCOPE_IDENTITY();"
cmdInsertCerereOferta.Parameters.Add("#IDFurnizor", SqlDbType.Int).Value = CInt(Me.t_IDFurnizor.Text)
cmdInsertCerereOferta.Parameters.Add("#NrCerereOferta", SqlDbType.Int).Value = CInt(Me.t_NumarCerereOferta.Text)
cmdInsertCerereOferta.Parameters.Add("#DataCerereOferta", SqlDbType.Date).Value = CDate(Me.t_DataCerereOferta.Text)
cmdInsertCerereOferta.Parameters.Add("#IDModTransCerereOferta", SqlDbType.Int).Value = 1
cmdInsertCerereOferta.Parameters.Add("#ObservatiiCerereOferta", SqlDbType.NVarChar).Value = Me.t_ObservatiiCerereOferta.Text
Dim IDCerereOferta As Integer = cmdInsertCerereOferta.ExecuteScalar
Dim ListaPieseCerereOferta = Me.CerereOfertaDataSet.ListaPieseCerereOferta.AsEnumerable
Dim ListaNecesarePePiesa = Me.CerereOfertaDataSet.NecesarePeOferta.AsEnumerable
Dim PieseOferta = From q In ListaPieseCerereOferta _
Select q
Dim cantTotalaPiese = Aggregate q In ListaPieseCerereOferta _
Into Sum(q.Cantitate)
Dim salvat As Integer = 0
Dim curIDPiesaDeSchimb As Integer
For Each piesa In PieseOferta
curIDPiesaDeSchimb = piesa.IDPiesaDeSchimb
Dim NecesarePePiesa = From p In ListaNecesarePePiesa _
Select p _
Order By p.IDNecesar Descending
Dim curIDNecesar As Integer
For Each necesar In NecesarePePiesa
curIDNecesar = necesar.IDNecesar
Dim cmdInsertPiesaCerereOferta As SqlCommand = conn.CreateCommand
cmdInsertPiesaCerereOferta.Transaction = sqlTrans
cmdInsertPiesaCerereOferta.CommandText = "INSERT INTO CereriOferte (IDCerereOferta,IDPiesaDeSchimb,Cantitate,UM,Observatii)" + _
" VALUES (#IDCerereOferta,#IDPiesaDeSchimb,#Cantitate,#UM,#Observatii);" + _
" SELECT SCOPE_IDENTITY();"
cmdInsertPiesaCerereOferta.Parameters.Add("#IDCerereOferta", SqlDbType.Int)
cmdInsertPiesaCerereOferta.Parameters.Add("#IDPiesaDeSchimb", SqlDbType.Int)
cmdInsertPiesaCerereOferta.Parameters.Add("#Cantitate", SqlDbType.Float)
cmdInsertPiesaCerereOferta.Parameters.Add("#UM", SqlDbType.NVarChar)
cmdInsertPiesaCerereOferta.Parameters.Add("#Observatii", SqlDbType.NVarChar)
Dim cmdInsertNecesarCerereOferta As SqlCommand = conn.CreateCommand
cmdInsertNecesarCerereOferta.Transaction = sqlTrans
cmdInsertNecesarCerereOferta.CommandText = "INSERT INTO NecesareCereriOferte (IDPiesaNecesar,IDPiesaCerereOferta)" + _
" VALUES (#IDPiesaNecesar,#IDPiesaCerereOferta)"
cmdInsertNecesarCerereOferta.Parameters.Add("#IDPiesaNecesar", SqlDbType.Int)
cmdInsertNecesarCerereOferta.Parameters.Add("#IDPiesaCerereOferta", SqlDbType.Int)
Select Case curIDNecesar
Case 0
cmdInsertPiesaCerereOferta.Parameters("#IDCerereOferta").Value = IDCerereOferta
cmdInsertPiesaCerereOferta.Parameters("#IDPiesaDeSchimb").Value = curIDPiesaDeSchimb
cmdInsertPiesaCerereOferta.Parameters("#Cantitate").Value = 1
cmdInsertPiesaCerereOferta.Parameters("#UM").Value = piesa.UM
cmdInsertPiesaCerereOferta.Parameters("#Observatii").Value = ""
For i = 1 To necesar.Cantitate
cmdInsertPiesaCerereOferta.ExecuteNonQuery()
salvat += 1
Me.tsspb_SalvareCerereOferta.Value = CInt(100 * salvat / cantTotalaPiese)
Next
Case Is > 0
Me.PieseNecesarePeOfertaTableAdapter.Fill(Me.CerereOfertaDataSet.PieseNecesarePeOferta, curIDNecesar, curIDPiesaDeSchimb, CInt(necesar.Cantitate))
Dim ListaPieseNecesarePeOferta = Me.CerereOfertaDataSet.PieseNecesarePeOferta.AsEnumerable
Dim PieseNecesareOferta = From q In ListaPieseNecesarePeOferta _
Select q
For i = 1 To necesar.Cantitate
cmdInsertPiesaCerereOferta.Parameters("#IDCerereOferta").Value = IDCerereOferta
cmdInsertPiesaCerereOferta.Parameters("#IDPiesaDeSchimb").Value = curIDPiesaDeSchimb
cmdInsertPiesaCerereOferta.Parameters("#Cantitate").Value = 1
cmdInsertPiesaCerereOferta.Parameters("#UM").Value = piesa.UM
cmdInsertPiesaCerereOferta.Parameters("#Observatii").Value = ""
Dim insertedIDPiesaCerereOferta As Integer = cmdInsertPiesaCerereOferta.ExecuteScalar
cmdInsertNecesarCerereOferta.Parameters("#IDPiesaNecesar").Value = PieseNecesareOferta(i - 1).IDPiesaNecesar
cmdInsertNecesarCerereOferta.Parameters("#IDPiesaCerereOferta").Value = insertedIDPiesaCerereOferta
cmdInsertNecesarCerereOferta.ExecuteNonQuery()
salvat += 1
Me.tsspb_SalvareCerereOferta.Value = CInt(100 * salvat / cantTotalaPiese)
Next
End Select
Next
Next
sqlTrans.Commit()
MsgBox("Cererea de oferta a fost salvata.")
Catch ex As Exception
Try
sqlTrans.Rollback()
MsgBox("A aparut o eroare." + vbNewLine + ex.ToString + vbNewLine + "RollBack success. Cererea nu a fost salvata.")
Catch ex2 As SqlException
If Not sqlTrans.Connection Is Nothing Then
MsgBox("An exception of type " & ex2.GetType().ToString() & _
" was encountered while attempting to roll back the transaction.")
End If
End Try
Finally
If conn.State = ConnectionState.Open Then conn.Close()
End Try
Else
MsgBox("Nu ai completat integral cererea de oferta!")
End If
End Sub
query that locks:
SELECT TOP (100) PERCENT dbo.qry_NecesareNerezolvate.IDPiesaNecesar, COUNT(dbo.NecesareCereriOferte.IDPiesaCerereOferta) AS CereriOferte,
dbo.qry_NecesareNerezolvate.IDNecesar, dbo.qry_NecesareNerezolvate.IDPiesaDeSchimb, dbo.qry_NecesareNerezolvate.Cantitate
FROM dbo.qry_NecesareNerezolvate LEFT OUTER JOIN
dbo.NecesareCereriOferte ON dbo.qry_NecesareNerezolvate.IDPiesaNecesar = dbo.NecesareCereriOferte.IDPiesaNecesar
GROUP BY dbo.qry_NecesareNerezolvate.IDPiesaNecesar, dbo.qry_NecesareNerezolvate.IDNecesar, dbo.qry_NecesareNerezolvate.IDPiesaDeSchimb,
dbo.qry_NecesareNerezolvate.Cantitate
qry_NecesareNerezolvate:
SELECT TOP (100) PERCENT dbo.Necesare.IDPiesaNecesar, dbo.Necesare.IDNecesar, dbo.Necesare.IDPiesaDeSchimb, dbo.Necesare.Cantitate, dbo.Necesare.UM,
dbo.Necesare.Observatii
FROM dbo.Necesare LEFT OUTER JOIN
dbo.qry_NecesareComandateRezolvate ON dbo.Necesare.IDPiesaNecesar = dbo.qry_NecesareComandateRezolvate.IDPiesaNecesar
WHERE (dbo.qry_NecesareComandateRezolvate.IDPiesaNecesar IS NULL)
qry_NecesareComandateRezolvate:
SELECT dbo.Necesare.IDPiesaNecesar, dbo.NecesareComenzi.IDPiesaComanda, dbo.NecesareRezolvate.IDBonTransfer
FROM dbo.Necesare LEFT OUTER JOIN
dbo.NecesareComenzi ON dbo.Necesare.IDPiesaNecesar = dbo.NecesareComenzi.IDPiesaNecesar LEFT OUTER JOIN
dbo.NecesareRezolvate ON dbo.Necesare.IDPiesaNecesar = dbo.NecesareRezolvate.IDPiesaNecesar
WHERE (dbo.NecesareComenzi.IDPiesaComanda IS NOT NULL) OR
(dbo.NecesareRezolvate.IDBonTransfer IS NOT NULL)
for i=1: insert, select then insert is working
then i=2 and: INSERT into table2... is working but SELECT FROM table1 and table3... gets timeout...
I don't understand why!
PS: If I break the code before second run of SELECT FROM table3 then go to SSMS and run the select query it gets timeout too...
In your code sample below, you have the transaction open till the end of the For Loop.
It seems to me that when i =1 , the transaction gets opened and a insertion is made. Now when i=2 , the to be inserted row when i=1 is in uncomitted state and if your select is joining to the table1 the lock level would have escalated to table level and locked everything down. Move the commit to inside the for loop and check how it goes.
for i=1 to x
...
INSERT into table2
...
SELECT FROM table3
...
INSERT into table3
...
next i
sqltransaction.commit