[英]UPDATE query doesn't update in C# while it works in Access
當列中的值大於0時,我正在嘗試更新列,否則它將插入新行。
UPDATE查詢首先在Access中經過測試,並且可以正常工作,在C#中嘗試過,但沒有成功。
不知道在哪里尋找。 有幫助/提示嗎?
Reservation selection = (Reservation)lstbReservations.SelectedItem;
connection.Open();
command.CommandText = @"SELECT Service_Overzicht.OverzichtID, Service.ServiceID, Service.Beschrijving,
IIf(Service_Overzicht.Aantal Is Null,0,Service_Overzicht.Aantal) AS Aantal, Service.Prijs, Service.Categorie
FROM Service LEFT JOIN (SELECT * FROM Service_Overzicht WHERE OverzichtID = [@waarde])
AS OSF ON Service.ServiceID = OSF.ServiceID;";
command.Connection = connection;
command.Parameters.Add(new OleDbParameter("@waarde", OleDbType.Integer));
command.Parameters["@waarde"].Value = selection.Reserveringsnummer;
reader = command.ExecuteReader();
while(reader.Read())
{
if(reader.GetString(2) == "Douche Muntjes")
{
if(reader.GetInt32(3) == 0)
{
command1.CommandText = @"INSERT INTO Service_Overzicht (OverzichtID, ServiceID, Aantal) VALUES (@resID, @sID, @aantal)";
}
else
{
command1.CommandText = @"UPDATE Service_Overzicht
SET Aantal = @aantal
WHERE OverzichtID = @resID AND ServiceID = @sID";
}
command1.Connection = connection;
command1.Parameters.Add(new OleDbParameter("@resID", OleDbType.Integer));
command1.Parameters["@resID"].Value = selection.Reserveringsnummer;
command1.Parameters.Add(new OleDbParameter("@sID", OleDbType.Integer));
command1.Parameters["@sID"].Value = 1;
command1.Parameters.Add(new OleDbParameter("@aantal", OleDbType.Integer));
command1.Parameters["@aantal"].Value = nudShower.Value;
reader1 = command1.ExecuteReader();
if(reader1.HasRows)
{
MessageBox.Show("Something went wrong!");
}
else
{
MessageBox.Show("Services updated");
}
}
在OleDb中,通過查找名稱而不是查找位置可以檢索到參數。 您需要按照參數在查詢中出現的順序將其放入集合中。
通過反轉INSERT查詢中字段的順序,您可以為INSERT和UPDATE以相同順序插入參數。
if(reader.GetInt32(3) == 0)
{
command1.CommandText = @"INSERT INTO Service_Overzicht
(Aantal, OverzichtID, ServiceID)
VALUES ( @aantal, @resID, @sID)";
}
else
{
command1.CommandText = @"UPDATE Service_Overzicht
SET Aantal = @aantal
WHERE OverzichtID = @resID AND ServiceID = @sID";
}
command1.Parameters.Add("@aantal", OleDbType.Integer).Value = nudShower.Value;
command1.Parameters.Add("@resID", OleDbType.Integer).Value = selection.Reserveringsnummer;
command1.Parameters.Add("@sID", OleDbType.Integer).Value = 1;
command1.Connection = connection;
最后,使用ExecuteNonQuery調用並查看表示已更改的行數的返回值來執行UPDATE / INSERT / DELETE查詢。
調用ExecuteReader也是可行的,因為它執行傳遞的查詢,但是它嘗試構建OleDbDataReader來讀取假定返回的記錄集。
您沒有要通過更新查詢回讀的記錄,而只有一個數字。
int rows = command1.ExecuteNonQuery();
if(rows != 0)
....success....
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