Question

OleDbCommand cmd = new OleDbCommand("SELECT Stock FROM Products WHERE ID=" + ProductID + ";", conn); //run the database query
OleDbDataReader cusReader = cmd.ExecuteReader(); //read the result of the query
cusReader.Read();           
ProductStock = (int)cusReader.GetValue(0);
cusReader.Close();
MessageBox.Show((ProductStock).ToString()); // checks that the form is being accessed and the SELECT query works

OleDbCommand cmd1 = new OleDbCommand("UPDATE Products SET Stock=" + (ProductStock - 1) + "WHERE ID= " + ProductID +";", conn);

try
{
   if (cusReader.RecordsAffected > 0)
   {
      MessageBox.Show("no issue was experienced");
   }
   else
   {
      MessageBox.Show("An issue occured when decreasing stock");
   }
   cusReader.Close();
}
catch (Exception ex)
{
   MessageBox.Show("An error occured in query.\n" + ex.Message);
}

更新查询返回＆＃34;发生的问题＆＃34;信息。显示变量Productstock的消息框确实返回正确的值。有人可以解释如何解决这个问题吗？

Answer 1

在WHERE

中的+ "WHERE ID= " +之前放置一个空格

另外，请务必在ExecuteNonQuery上致电cmd1。

Answer 2

OleDbCommand cmd1 = new OleDbCommand("UPDATE Products SET Stock=" + (ProductStock - 1) + " WHERE ID= " + ProductID +";", conn);

请使用上述命令。

问题：库存值与

之间没有空格

Answer 3

请尝试这个。它应该工作

OleDbCommand cmd1 = new OleDbCommand("UPDATE Products SET Stock=" + (ProductStock - 1) + " WHERE ID= " + ProductID, conn);

Answer 4

尝试一次性更新（不要将select和update分开：有人可以在您执行之后修改数据 {{ 1}}但之前您已启动select），然后检查受影响的行。让你的SQL 可读以避免明显的错误。

update

SQL Update Query返回错误

4 个答案: