Decreasing a field

hi all am using vs2010
here is my connection string

Code:

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Dim MySQLConnection As MySqlConnection
        MySqlConnection = New MySqlConnection
        MySQLConnection.ConnectionString = "server=db4free.net;Port=3306; User ID=seifhatem; password=11; database=huaweiunlocking"
        MySqlConnection.Open()

        Dim MyAdapter As New MySqlDataAdapter
        Dim SqlQuary = "SELECT * From Users WHERE Username='" & usernametextbox.Text & "' AND password = '" & passwordtextbox.Text & "';"
        Dim Command As New MySqlCommand
        Command.Connection = MySqlConnection
        Command.CommandText = SqlQuary
        MyAdapter.SelectCommand = Command
        Dim Mydata As MySqlDataReader
        Mydata = Command.ExecuteReader
        If Mydata.HasRows = 0 Then
            MsgBox("Error During Login:Please Enter Valid Data")
        Else

        End If

---

I want a command that decreases the field called Credits in the database and i will write between else and end if
like if the user clicks the button it connects and decrease 1 credit thx in advance

What is the structure of the table?

ID,Username,Password and Credit(which i want yo decrease it)
Thx in asvance

What is the datatype of credit? So you're wanting to do an update statement to decrease by 1 every record returned by SqlQuary? Am I understanding your need correctly?

Yes u'r right and the type is varchar

is there a reason you're not using an integer datatype? it just holds numeric data, correct?

So you need to use an update query to decrease by one and as gtrahern suggested you may be better of using some numeric type.
So what is the problem you have?

Ok and after changing it to integer
How can i edit it using vb.net

Quote:

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Originally Posted by salmawy

Ok and after changing it to integer
How can i edit it using vb.net

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Fetch the value to a variable.
Update the value of the variable by subtracting 1 from it.
Update the table with the value of the variable.

Do you want the code for this?

What is thecode to do these things

Because this is my first time to work with sql

Quote:

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Originally Posted by salmawy

What is thecode to do these things

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Running an update statement is the easiest way to do it.

UPDATE USERS SET CREDIT = CREDIT -1 WHERE USERNAME = 'USER'

You'll need to replace some of the values in the sql statement. To figure out how to execute this statement, look up the tutorials on this forum.

Do i need to excute it using
Sql qyary

Quote:

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Originally Posted by salmawy

Do i need to excute it using
Sql qyary

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To execute this SQL Query, you'll need a connection string, a command object and a parameter object.

Follow this link: http://www.vbforums.com/showthread.php?t=469872
OR
this one.

http://msdn.microsoft.com/en-us/libr...ogmsdn_topic5c

I am usingmysql connecter/net 6.0.7 as refrence and the connection string is in post 1 i did the connection

I don't think there are many differences.
Just use a mysql tutorial.