Private Sub ListBox_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ListBox.SelectedIndexChanged
Dim connect As String = "server=localhost;user=root;password=Password;database=giordydatabase"
Dim sqlQuery As String = "SELECT firstName, lastName FROM students WHERE name =#firstName"
Using sqlConn As New MySqlConnection(connect)
Using sqlComm As New MySqlCommand()
With sqlComm
.Connection = sqlConn
.CommandText = sqlQuery
.CommandType = CommandType.Text
.Parameters.AddWithValue("#firstName")
End With
Try
sqlConn.Open()
Dim sqlReader As MySqlDataReader = sqlComm.ExecuteReader()
While sqlReader.Read()
ListBox.Text = sqlReader("Name").ToString()
End While
Catch ex As MySqlException
' add your exception here '
End Try
End Using
End Using
That's what I have done so far, I would like know how to retrieve the data and putting it into a ListBox.
Try changing this line
ListBox.Text = sqlReader("Name").ToString()
To
ListBox.Items.Add(sqlReader("Name").ToString())
Related
Dim Conn As MySqlConnection
Dim Command As MySqlCommand
Dim Reader As MySqlDataReader
Dim server As String = "serverxxxxxxxx.1;user=root;database=xxxxxxxxx"
Public Sub testing()
Conn = New MySqlConnection
Conn.ConnectionString = server
Dim datecompare As String = Date.Today.ToString("yyyy-MM-dd hh:mm:ss")
Dim primarykey1 As String = ""
Dim primarykey2 As String = ""
Try
If Not Conn.State = ConnectionState.Open Then
Conn.Open()
End If
Dim Query1 As String
Query1 = "Select * From `tblborrow` Where `DueDate` = '" & datecompare & "'"
Command = New MySqlCommand(Query1, Conn)
Reader = Command.ExecuteReader
While Reader.Read
primarykey1 = Reader.GetInt32("BorrowID")
Try
If Not Conn.State = ConnectionState.Open Then
Conn.Open()
End If
Dim query2 As String
query2 = "Update `tblborrow` Set `Remarks` = '" & "Due Date" & "' Where `BorrowID` = '" & primarykey1 & "'"
Command = New MySqlCommand(query2, Conn)
Reader = Command.ExecuteReader
Reader.Close()
Conn.Close()
Catch ex As Exception
MsgBox(ex.Message)
End Try
'end of duedate
End While
Reader.Close()
Conn.Close()
Catch ex As Exception
MsgBox(ex.Message)
End Try
'for OVER DUE
Try
If Not Conn.State = ConnectionState.Open Then
Conn.Open()
End If
Dim Query1 As String
Query1 = "Select * From `tblborrow` Where `DueDate` < '" & datecompare & "'"
Command = New MySqlCommand(Query1, Conn)
Reader = Command.ExecuteReader
While Reader.Read
primarykey2 = Reader.GetInt32("BorrowID")
Try
If Not Conn.State = ConnectionState.Open Then
Conn.Open()
End If
Dim query2 As String
query2 = "Update `tblborrow` Set `Remarks` = '" & "Over Due" & "' Where `BorrowID` = '" & primarykey2 & "'"
Command = New MySqlCommand(query2, Conn)
Reader = Command.ExecuteReader
Reader.Close()
Conn.Close()
Catch ex As Exception
MsgBox(ex.Message)
End Try
'end of Over Due
End While
Reader.Close()
Conn.Close()
Catch ex As Exception
MsgBox(ex.Message)
End Try
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
Call testing()
End Sub
I created a public sub that will select and update the Remarks in my database based on the borrowID(this is auto increment). The save date in DueDate and compare i declare with the current time today, but every time i click the button where i saved the code i get this error There is already an openDataReaderassociated with this connection which must be closed first
i double checked my code and didn't miss to put reader.close() after every conn.close() or i don't know maybe i missed..
i tried some several changes in my code but still i get the same error.
can some help me and build my code? .. thanks.
Try to use different variable for the readers, maybe Reader1 and Reader2.
It's probably because you used the same reader to execute different query hence the already open datareader error.
You try to open the same book which is already open. At least make it a different book.
You are attempting to open 2 readers on a single connection. See the double headed arrows.
Reader = Command.ExecuteReader'<<----
While Reader.Read
primarykey1 = Reader.GetInt32("BorrowID")
Try
If Not Conn.State = ConnectionState.Open Then
Conn.Open()
End If
Dim query2 As String
query2 = "Update `tblborrow` Set `Remarks` = '" & "Due Date" & "' Where `BorrowID` = '" & primarykey1 & "'"
Command = New MySqlCommand(query2, Conn)
Reader = Command.ExecuteReader '<<----
If you break your code into logical units with only a single thing happening in each method it is a bit easier to see where things go wrong.
Keeping your database objects local to the methods where they are used allows you to be sure they are closed and disposed. Using...End Using blocks handle this for you even if there is an error.
Notice, in the 2 Update methods, the parameters are added outside the For loop and only the value that changes is set inside the loop.
Dim ConString As String = "serverxxxxxxxx.1;user=root;database=xxxxxxxxx"
Public Sub GetPKs()
Dim pkList As New List(Of Integer)
Dim DueDate As String = Date.Today.ToString("yyyy-MM-dd hh:mm:ss")
Using Conn As New MySqlConnection(ConString),
cmd As New MySqlCommand("Select BorrowID From tblborrow Where DueDate = #DueDate")
cmd.Parameters.Add("#DueDate", MySqlDbType.VarChar, 100).Value = DueDate
Conn.Open()
Using reader As MySqlDataReader = cmd.ExecuteReader
While reader.Read
pkList.Add(reader.GetInt32("BorrowID"))
End While
End Using
End Using
UpdateRemarks(pkList, DueDate)
End Sub
Private Sub UpdateRemarks(pks As List(Of Integer), DueDate As String)
Using con As New MySqlConnection(ConString),
cmd As New MySqlCommand("Update tblborrow Set Remarks = #DueDate Where BorrowID = #PK", con)
With cmd.Parameters
.Add("#DueDate", MySqlDbType.VarChar, 100).Value = DueDate
.Add("#PK", MySqlDbType.Int32)
End With
con.Open()
For Each i In pks
cmd.Parameters("#PK").Value = i
cmd.ExecuteNonQuery()
Next
End Using
End Sub
Private Sub GetOverduePKs()
Dim pkList As New List(Of Integer)
Using cn As New MySqlConnection(ConString),
cmd As New MySqlCommand("Select BorrowID From tblborrow Where DueDate < #DueDate")
cmd.Parameters.Add("#DueDate", MySqlDbType.VarChar, 100).Value = Date.Today.ToString("yyyy-MM-dd hh:mm:ss")
cn.Open()
Using reader = cmd.ExecuteReader
While reader.Read
pkList.Add(reader.GetInt32("BorrowID"))
End While
End Using
End Using
UpdateOverdueRemarks(pkList)
End Sub
Private Sub UpdateOverdueRemarks(pks As List(Of Integer))
Using cn As New MySqlConnection(ConString),
cmd As New MySqlCommand("Update tblborrow Set Remarks = 'Over Due' Where BorrowID = #PK")
cmd.Parameters.Add("#PK", MySqlDbType.Int32)
cn.Open()
For Each i In pks
cmd.Parameters("#PK").Value = i
cmd.ExecuteNonQuery()
Next
End Using
End Sub
Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
GetPKs()
GetOverduePKs()
End Sub
use 2 connections CONN and CONN2, with the same parameters, use CONN to open the QUERY1 reader. While reading, use CONN2 to create the 2nd query. Note that this works for MySQL. MS-Access can handle multiple commands in one connection, MySql cannot and needs separate connections. Sqlite cannot handle 2 simultanuos connections. there you have to use in incore temporary array or list. From a working program:
Dim DbConn As New MySqlConnection(SqlProv)
Dim DbConn2 As New MySqlConnection(SqlProv)
-
Dim SQLsfSelect As String = "SELECT CollSeq FROM ToBeIndexed WHERE CollCode = #CollCode"
Dim DRsfSelect As MySqlDataReader = Nothing
Dim DCsfSelect As MySqlCommand
Dim sfSelP1 As New MySqlParameter("#CollCode", MySqlDbType.VarChar, 4)
DCsfSelect = New MySqlCommand(SQLsfSelect, DbConn)
-
Dim SQLasSelect As String = "SELECT DISTINCT CollSeq FROM Data WHERE CollCode = #CollCode ORDER BY CollSeq"
Dim DRasSelect As MySqlDataReader = Nothing
Dim DCasSelect As MySqlCommand
Dim asSelP1 As New MySqlParameter("#CollCode", MySqlDbType.VarChar, 4)
DCasSelect = New MySqlCommand(SQLasSelect, DbConn2)
-
DbConn.Open()
sfSelP1.Value = CurCollCode
CollSeqToIdxC.Clear()
Try
DRsfSelect = DCsfSelect.ExecuteReader()
Do While (DRsfSelect.Read())
CollSeq = GetDbIntegerValue(DRsfSelect, 0)
DbConn2.Open()
asSelP1.Value = CurCollCode
Try
DRasSelect = DCasSelect.ExecuteReader()
Do While (DRasSelect.Read())
CollSeq = GetDbIntegerValue(DRasSelect, 0)
CollSeqToIdxC.Add(CollSeq, CStr(CollSeq))
Loop
Catch ex As Exception
MsgBox(ex.ToString(), , SysMsg1p(402, CurCollCode))
Finally
If Not (DRasSelect Is Nothing) Then
DRasSelect.Close()
End If
End Try
DbConn2.Close()
Loop
Catch ex As Exception
MsgBox(ex.ToString(), , SysMsg1p(403, CurCollCode))
Finally
If Not (DRsfSelect Is Nothing) Then
DRsfSelect.Close()
End If
End Try
DbConn.Close()
Im trying to connect to mySql, but I have problem locating where im doing wrong.
My form contain e a label that is a number thats going to be posted to Score and a textbox where the user typed their name to be posted in Navn.
My code so far is:
Imports System
Imports System.Data
Imports System.Data.SqlClient
Public Class Form1
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim connect As New SqlConnection("Data Source = mysqlAdress;Network Library= DBMSSOCN;Initial Catalog=**;User ID=**;Password=**;")
Dim query As String = "INSERT INTO 2048 VALUES(#score, #name)"
Dim command As New SqlCommand(query, connect)
command.Parameters.Add("#score", SqlDbType.Int).Value = Label1.Text
command.Parameters.Add("#navn", SqlDbType.VarChar).Value = TextBox1.Text
connect.Open()
connect.Close()
End Sub
Your table name should be enclosed in backticks like this:
Dim query As String = "INSERT INTO `2048` VALUES(#score, #name)"
Also try to avoid table names with such naming conventions ie., only numbers.
Also you are opening and closing the connection simultaneously.
connect.Open()
connect.Close()
Try like this:
Private Sub Button2_Click(sender As Object, e As EventArgs) Handles Button2.Click
Dim connectionString As String = "Data Source = mysqlAdress;Network Library= DBMSSOCN;Initial Catalog=**;User ID=**;Password=**;"
Using SQLConnection As New MySqlConnection(connectionString)
Using sqlCommand As New MySqlCommand()
With sqlCommand
.CommandText = "INSERT INTO `2048` VALUES(#score, #name)"
.Connection = SQLConnection
.CommandType = CommandType.Text
.Parameters.AddWithValue("#score", Label1.Text)
.Parameters.AddWithValue("#name", TextBox1.Text)
End With
Try
SQLConnection.Open()
sqlCommand.ExecuteNonQuery()
Catch ex As MySqlException
MsgBox ex.Message.ToString
Finally
SQLConnection.Close()
End Try
End Using
End Using
End Sub
im trying to retrieve mysql data with specific column and show to textbox in vb.net. what should i do in retrieving it?
Dim connect As New MySqlConnection("server=localhost; user id=root; password= ; database=ticketing_system;")
connect.Open()
Dim sqladapter As New MySqlDataAdapter
Dim sqlcmd As New MySqlCommand
Dim dr As MySqlDataReader
Dim dt As New DataTable
sqlcmd = New MySqlCommand("SELECT * complaint WHERE tran_no='" & lbltranno.Text & "'")
**THEN? WHAT SHOULD I DO TO DISPLAY DATA? PLEASE HELP**
connect.Close()
You are simply missing the Execution method. It depends on what kind of result you want. If you only want the first result from the query (first row and first column) then use sqlcmd.ExecuteScalar().
If you want all the results you'll have to load that into a MySqlDataReader using the method sqlcmd.ExecuteReader()
Using ExecuteReader() :
Dim connect As New MySqlConnection("server=localhost; user id=root; password= ; database=ticketing_system;")
connect.Open()
Dim sqladapter As New MySqlDataAdapter
Dim sqlcmd As New MySqlCommand
Dim dr As MySqlDataReader
Dim dt As New DataTable
sqlcmd = New MySqlCommand("SELECT * complaint WHERE tran_no='" & lbltranno.Text & "'")
dr = sqlcmd.ExecuteReader()
dt.Load(dr)
'Useable datatable in dt variable...
connect.Close()
Using ExecuteScalar() :
Dim connect As New MySqlConnection("server=localhost; user id=root; password= ; database=ticketing_system;")
connect.Open()
Dim sqladapter As New MySqlDataAdapter
Dim sqlcmd As New MySqlCommand
Dim dr As String
Dim dt As New DataTable
sqlcmd = New MySqlCommand("SELECT [COLUMN NAME] complaint WHERE tran_no='" & lbltranno.Text & "'")
dr = sqlcmd.ExecuteScalar()
'dr now contains the value of [COLUMN NAME] for the first returned row.
connect.Close()
You can try this:
Dim connString As String = "server=localhost; user id=root; password=[REPLACE WITH PASSWORD] ; database=ticketing_system;"
Dim sqlQuery As String = "SELECT * from complaint WHERE tran_no='" & lbltranno.Text & "'";
Using sqlConn As New MySqlConnection(connString)
Using sqlComm As New MySqlCommand()
With sqlComm
.Commandtext = sqlQuery
End With
Try
sqlConn.Open()
Dim sqlReader As MySqlDataReader = sqlComm.ExecuteReader()
While sqlReader.Read()
Label1.Text = sqlReader("Name").ToString()
Label2.Text = sqlReader("Points").ToString()
End While
Catch ex As MySQLException
' add your exception here '
End Try
End Using
End Using
Imports System.Data.SqlClient
Public Class Form1
Dim c As New SqlConnection("Data Source=SONY;Initial Catalog=msdb;Integrated Security=True")
Dim cmd As New SqlCommand
Dim da As New SqlDataAdapter
Dim dr As SqlDataReader
Dim ds, ds1 As New DataSet
Private Sub btnsub_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btnsub.Click
Try
ds.Clear()
c.Open()
cmd = New SqlCommand("select Sub_Name from Subject_Detail WHERE Course='" + txtcourse.Text + "'", c)
da = New SqlDataAdapter(cmd)
da.Fill(ds, "Subject_Detail")
Label1.Text = ds.Tables(0).Rows(0).Item(0)
Label2.Text = ds.Tables(0).Rows(1).Item(0)
Label3.Text = ds.Tables(0).Rows(2).Item(0)
Label4.Text = ds.Tables(0).Rows(3).Item(0)
Label5.Text = ds.Tables(0).Rows(4).Item(0)
Label6.Text = ds.Tables(0).Rows(5).Item(0)
Catch ex As Exception
MsgBox(ex.Message)
Finally
c.Close()
End Try
End Sub
End Class
'This code display all subject name from the table into labels.This might be helped.
Try this one, i always use this code, that's why i'm pretty sure that this will work...
Imports MySql.Data
Imports MySql.Data.MySqlClient
Dim connect As New MySqlConnection("server=localhost;uid=root;database=ticketing_system;pwd=;")
connect.Open()
Dim sqlcmd As New MySqlCommand("SELECT * complaint WHERE tran_no='" & lbltranno.Text & "'")
Dim sqladapter As New MySqlDataAdapter(sqlcmd)
Dim dt As New DataTable
sqladapter.Fill(dt)
Datagridview1.Datasource = dt
connect.Close()
Imports MySql.Data
Imports MySql.Data.MySqlClient
Dim dbConnection As New MySqlConnection("server=localhost;uid=youruser;database=yourdb;pwd=password")
try
dbConnection.open
catch ex as exception
debug.print(ex.message)
end try
using Adapter as new mysqldataadapter("select * from yourtable where yourcolumn = 'yourvalue'", dbConnection)
using Table as new datatable
Adapter.fill(Table)
Datagridview.datasource = table
end using
end using
dbConnection.close
Imports MySql.Data.MySqlClient
''--- Data Reader Example
private _cn as New MySqlConnection( _
"data source=server; database=databaseName; user id=username; password=password")
private cmd as new MySqlCommand
private dr as MySqlDataReader
With cmd
.Command = "select Name, Address from Clients"
.CommandType = CommandType.Text
.Connection = cn
End With
cn.Open()
dr = cmd.ExecuteReader
While dr.Read
'' use dr(0) for get Name, and dr(1) to get Address for this example
Console.WriteLine(dr(0) & " - " & dr(1))
Console.WriteLine(dr("Name").ToString() & " - " & dr("Address").ToString())
End While
dr.Close
cn.Close
Dim MysqlConn As MySqlConnection
Dim connectionString As String = "Server=-host-ip-;Database=Mysqldb;Uid=user;Pwd=password"
MysqlConn = New MySqlConnection(connectionString)
Try
Dim Mysqlcmd As New MySqlCommand("SELECT * FROM Mysqldb.table WHERE col='" & Label6.Text & "'", MysqlConn)
Dim dt As New DataTable
Dim Mysqladapter As New MySqlDataAdapter()
MysqlConn.Open()
Mysqladapter.SelectCommand = Mysqlcmd
Mysqladapter.Fill(dt)
DataGridView1.DataSource = dt
MessageBox.Show("Connection to Database has been opened.")
MysqlConn.Close()
Catch myerror As MySqlException
MessageBox.Show("Cannot connect to database: " & myerror.Message)
Finally
MysqlConn.Dispose()
End Try
The key is to add the connection at the end of the mysql query as in line 6
I used a variation of the code given in this thread with Visual Basic 2015. I found I needed a 2nd argument in the MySqlCommand statement, namely the MySqlConnection variable ("connect" in some of the examples). See thread: Connection must be valid and open VB.Net
Thanks for the help.
I am new in VB.NET and as well as SQL. I want to update records in my database. I made a dummy in my database.
Example the values are: ID = 1, name=Cath, age=21
In my interface made in VB.NET, I update the values example : name = txtName.Text and age = txtAge.Text where ID = 1. This is in my main form. In my main form, I have "view" button informing that by clicking that button, new form would pop up and would view the updated values by the user. The program does not have any errors except that when I want to update again the values in my SQL, It record BUT when I click "view" button again, It will show the previous inputted by the user (the first update upon running the interface). What should be the solution?
This is my code:
Mainform:
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
SQLConnection.ConnectionString = ServerString
Try
If SQLConnection.State = ConnectionState.Closed Then
SQLConnection.Open()
MessageBox.Show("Successful connection")
Else
'SQLConnection.Close()
MessageBox.Show("Connection is closed")
End If
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
Public Sub SaveNames(ByRef SQLStatement As String)
Dim cmd As MySqlCommand = New MySqlCommand
With cmd
.CommandText = SQLStatement
.CommandType = CommandType.Text
.Connection = SQLConnection
.ExecuteNonQuery()
End With
MsgBox("Successfully Added!")
End Sub
Private Sub cmdSave_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdSave.Click
Dim date_now As String
date_now = Format(dtpDate.Value, "yyyy-MM-dd")
Dim SQLStatement As String = "UPDATE people SET name='" & txtName.Text & "', date ='" & date_now & "' WHERE 1"
SaveNames(SQLStatement)
End Sub
Form 2: (where the updated data would be viewed)
Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
SQLConnection.ConnectionString = ServerString
Try
If SQLConnection.State = ConnectionState.Closed Then
SQLConnection.Open()
'====retrieve / update values in database=============
Dim SQLStatement As String = "SELECT name, date FROM people"
ViewInfos(SQLStatement)
Else
'SQLConnection.Close()
MessageBox.Show("Connection is closed")
End If
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
Public Sub ViewInfos(ByRef SQLStatement As String)
Dim cmd As MySqlCommand = New MySqlCommand
With cmd
.CommandText = SQLStatement
.CommandType = CommandType.Text
.Connection = SQLConnection
.ExecuteNonQuery()
End With
'--read the records in database in phpmyadmin gui---
Dim myReader As MySqlDataReader = cmd.ExecuteReader
If myReader.Read Then
lblName.Text = myReader.GetString(0)
lblDate.Text = myReader.GetString(1)
End If
myReader.Close()
MsgBox("Records Successfully Retrieved")
End Sub
Any help would be appreciated. Thanks!
You are leaving your connection string open when you update sql, thus when you try to retrieve the data, your condition closes the connection without reading the data or updating your textboxes.
Take out the .ExecuteNonQuery() from the ViewInfos() method.
Refer to your forms via variables not via the form name:
Dim myForm as New Form2()
myForm.Show()
Im very new to Visual Basic (using visual studio 2010). Im just doing some tests to connect to a mysql database.
I do not know how to call these values once I have made the sql query.
How do I go about this, i.e. to show the values on the labels on a form?
Code:
Imports MySql.Data.MySqlClient
Public Class Form1
Dim ServerString As String = "Server = localhost; User Id = root; database = CALIBRA"
Dim SQLConnection As MySqlConnection = New MySqlConnection
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
SQLConnection.ConnectionString = ServerString
Try
If SQLConnection.State = ConnectionState.Closed Then
SQLConnection.Open()
MsgBox("Successfully connected to MySQL database.")
Else
SQLConnection.Close()
MsgBox("Connection is closed.")
End If
Catch ex As Exception
MsgBox(ex.ToString)
End Try
End Sub
Public Sub calibra_query(ByRef SQLStatement As String)
Dim cmd As MySqlCommand = New MySqlCommand
With cmd
.CommandText = SQLStatement
.CommandType = CommandType.Text
.Connection = SQLConnection
.ExecuteNonQuery()
End With
SQLConnection.Close()
MsgBox("Records Successfully Retrieved")
SQLConnection.Dispose()
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim SQLStatement As String = "SELECT Auto1, Auto2, TotalWeight FROM txticket WHERE TicketCode = '12210'"
calibra_query(SQLStatement)
Dim Automobile1, Automobile2, TotalWgt As Long
SOMETHING MISSING HERE
SOMETHING MISSING HERE
Label2.Text = Automobile1.ToString()
Label2.Text = Automobile2.ToString()
Label2.Text = TotalWgt.ToString()
End Sub
End Class
What do I put in the "SOMETHING MISSING HERE"? Much appreciation.
You will need a data reader in order to read the content of what is returned from the sql query. Your Sub calibra_query, is executing a nonreader, that isn't going to do what you need. You only want to use executeNonReader for things that you don't need a result from. (Like an Update statement for example)
You want something a bit more like this:
Dim cmd As MySqlCommand = New MySqlCommand
With cmd
.CommandText = SQLStatement
.CommandType = CommandType.Text
.Connection = SQLConnection
End With
Dim myReader as MySqlDataReader = myCommand.ExecuteReader
If myReader.Read Then
TextBox1.Text = myReader.GetString(0)
TextBox2.Text = myReader.Getstring(1)
TextBox3.Text = myReader.GetInt32(2)
End If
myReader.Close()
SQLConnection.Close()
MsgBox("Records Successfully Retrieved")
SQLConnection.Dispose()
I am assuming the types of the 3 fields in your query, and just outputting it to text boxes to give you the idea. That also assumes that you are only going to get one record as a result.
(Edit: to fix formatting)