Как установить переменную группу в mysql и визуальную основу c?

Question

Как правильно установить @ dategiven1?

set @dategiven1 = ('1','2','3');
set @dategive4 = 2020;
set @activity = "Aerial Cable Installation";

SELECT id, billingreference, opac, projectorder, projectlocation, headedby, dategiven 
FROM project_info 
WHERE MONTH(dategiven) IN (@dategiven1) 
  AND YEAR(dategiven) = @dategiven4 
  AND id IN ( SELECT project_id 
              FROM manpower_project 
              WHERE activity = @activity )

и как я могу применить эту визуальную основу c?

Спасибо, беспокойство по моему необъяснимому вопросу: (

Answer 1

Кажется, что метод Month в MySql возвращает целое число, поэтому вам понадобятся цифры, разделенные запятыми, заключенные в парантезе. Параметр передает одно значение, поэтому параметры здесь не подходят. Вам нужно построить строку и объединить ее в операторе select.

Private Function InClause(Months As Integer(), Year As Integer, Activity As String) As DataTable
    'StringBuilder is mutable so it save creating a new string and tossing the old one on each iteration
    'Start the string out with the opening parenthesis
    Dim BuildInClause As New StringBuilder("(")
    'loop through each element in the array and add it to the string builder along with a comma
    For Each m In Months
        BuildInClause.Append(m & ",")
    Next
    'convert the StringBuilder to a string, Trim off the final comma and add the closing parenthesis.
    Dim str = BuildInClause.ToString.Trim(","c) & ")"
    'Check what the string looks like
    Debug.Print(str)
    Dim dt As New DataTable
    'The Using...End Using block ensures that you connection and command are closed and disposed even if there is an error
    Using cn As New MySqlConnection("Your connection String"),
            cmd As New MySqlCommand("Select id, billingreference, opac, projectorder, projectlocation, headedby, dategiven 
                From project_info
                Where Month(dategiven) In " & str &
                " And YEAR(dategiven) = @dategiven4 
                And id IN ( SELECT project_id From manpower_project 
                  Where activity = @activity ))", cn)
        cmd.Parameters.Add("@dategiven4", MySqlDbType.Int32).Value = Year
        cmd.Parameters.Add("@activity", MySqlDbType.String).Value = Activity
        cn.Open()
        dt.Load(cmd.ExecuteReader)
    End Using
    Return dt
End Function

Использование:

Private Sub Button1_Click(sender As Object, e As EventArgs) Handles Button1.Click
    Dim intArray = {1, 2, 3}
    Dim dt = InClause(intArray, 2020, "Aerial Cable Installation")
    DataGridView1.DataSource = dt
End Sub