使用组合框特定选项显示数据库中的数据：ALL SIZES

Question

Interface I'm trying to display data from the database to DataGridView which I successfully did but I want to display in two ways: 1) to display all records and 2) to display specified records. I was able to display specified records using two Combo Boxes: brand and sizes by specifying from their dropdown list and data are shown on the DataGridView. But I now want to display ALL BRANDS and ALL SIZES from the drop-down list but it's not displaying; it only displays either of the queries. How can put the code display based on the selection of the dropdown list?

I have put an if statement that checks if the user has selected ComboBox1: ALL TYRES and ComboBox2: ALL TYRES then it should execute ALL QUERY. If not and the user has selected just one type of brand and size then it would display just that with another query.

The interface: This is the code:

Private Sub btnSearch_Click(sender As Object, e As EventArgs) Handles btnSearch.Click
    MysqlConn = New MySqlConnection
    MysqlConn.ConnectionString = "server=localhost;userid=root;password=root;database=golden_star"

    ''connecting data grid with the database
    Dim Sda As New MySqlDataAdapter
    Dim dbdataset As New DataTable
    Dim bSource As New BindingSource


    Try
        MysqlConn.Open()
        Dim Query As String
        Dim All As String

        If ComboBox1.Text = "ALL TYRES" & ComboBox2.Text = "ALL SIZES" Then
            All = "select * from golden_star.sales"
            Command = New MySqlCommand(All, MysqlConn)

        End If

       Query = "select sale_id,date,brand,size,selling_unit_price,cost_unit_price,quantity,cost_of_goods,profit,total_cost_price from golden_star.sales where brand = '" + ComboBox1.Text + "' and size = '" + ComboBox2.Text + "' "

        Command = New MySqlCommand(Query, MysqlConn)







        Sda.SelectCommand = Command
        Sda.Fill(dbdataset)
        bSource.DataSource = dbdataset
        DataGridView1.DataSource = bSource
        Sda.Update(dbdataset)


        MysqlConn.Close()
    Catch ex As MySqlException
        MessageBox.Show(ex.Message)

    Finally
        MysqlConn.Dispose()
    End Try

End Sub

Answer 1

Your SQL commands are not selecting the same columns.

All = "select * from golden_star.sales"

Query = "select sale_id,date,brand,size, selling_unit_price, cost_unit_price, quantity, cost_of_goods,profit,total_cost_price from golden_star.sales where brand = '" + ComboBox1.Text + "' and size = '" + ComboBox2.Text + "' "

How have you defined the grids? Are the columns being created dynamically or are they fixed?

Try changing the All query to select the same columns as the other query.

All = "select sale_id,date,brand,size, selling_unit_price, cost_unit_price, quantity, cost_of_goods,profit,total_cost_price from golden_star.sales"

If this doesn't work, please show the new code (with the else statements) and the gridview definition. Also check to see if "ALL TYRES" is defined in your combobox. (Should it be TYPES?)

I am guessing this is a training assignment. If this is something that will actually be used on a public website, you need to change the query. It is not safe to concatenate strings in the SQL command.