Spróbuj np. taki zapis dla dateTimePicker-a
private void Form1_Load(object sender, EventArgs e)
{
dateTimePicker1.Format = DateTimePickerFormat.Custom;
dateTimePicker1.CustomFormat = "dd";
}
i skorzystaj np. z DAY [ MONTH ]
...
connect.Open();
string sql = "SELECT time, sprzedaz FROM sprzedaz1 WHERE DAY(time) = " + dateTimePicker1.Text;
MySqlDataAdapter da = new MySqlDataAdapter(sql, connect);
DataSet ds = new DataSet();
...
lub tylko
...
connect.Open();
string sql = "SELECT time, sprzedaz FROM sprzedaz1 WHERE DAY(time) = " + dateTimePicker1.Value.Day;
MySqlDataAdapter da = new MySqlDataAdapter(sql, connect);
DataSet ds = new DataSet();
...
BTW, sprawdź na tej stronie wynik z użyciem DAY.
Przykłady do testów.
1.
SELECT * FROM Orders
2.
SELECT * FROM Orders WHERE DAY(OrderDate) = '06'
3.
SELECT * FROM Orders WHERE DAY(OrderDate) = 6
4.
SELECT * FROM Orders WHERE DAY(OrderDate) = 6 AND MONTH(OrderDate) IN (9,12)