您好我正在使用此代码从MySQL数据库的5个不同表中获取所需的数据。
private void goDateBtn_Click(object sender, EventArgs e)
{
reportList.Items.Clear();
var db = new DBConnect();
MySqlCommand cmd = null;
MySqlDataReader dr = null;
double totalsales = 0;
try
{
if (db.OpenConnection() == true)
{
string cmdstr = "SELECT ol.*, o.*, m.* "+
"FROM orderlist ol "+
"INNER JOIN orderdb o ON ol.order_ID = o.order_ID "+
"INNER JOIN menudb m ON ol.menu_ID = m.menu_ID "+
"INNER JOIN recipelist r ON r.menu_ID = m.menu_ID "+
"INNER JOIN "+
"( SELECT stock_ID, SUM(stock_pricePerPiece) menu_cost "+
"FROM stocksdb "+
"GROUP BY stock_ID )"+
"s ON r.stock_ID = s.stock_ID "+
"WHERE o.order_date >= #" + fromDate.Value.Date + "# AND " +
"o.order_date <= #" + toDate.Value.Date + "#";
cmd = new MySqlCommand(cmdstr, db.mycon);
dr = cmd.ExecuteReader();
string[] info = new string[20];
while (dr.Read())
{
info[1] = (dr["order_ID"].ToString());
info[2] = (dr["order_date"].ToString());
info[3] = (dr["menu_name"].ToString());
info[4] = (dr["menu_cost"].ToString());
info[5] = (dr["menu_price"].ToString());
info[6] = (Convert.ToDouble(info[5]) - Convert.ToDouble(info[4])).ToString("#0.00");
this.reportList.Items.Add(new ListViewItem(new string[] { info[1], info[2], info[3], info[4], info[5], info[6] }));
totalsales += Convert.ToDouble(info[6]);
}
}
}
catch (MySqlException ex)
{
MessageBox.Show(ex.Message);
}
finally
{
if (dr != null)
{
dr.Close();
}
db.CloseConnnection();
}
totalSalesTxtBox.Text = totalsales.ToString("#0.00");
MessageBox.Show("SALES REPORT FINISHED!");
}
我真的不知道我做错了什么，特别是在sql字符串中，最后INNER JOIN应该将stock_pricePerPiece表中的所有stocksdb加起来，其中股票是在同一菜单上使用，因此在menu_ID表中具有相同的recipedb。
我收到dr = cmd.ExecuteReader();
答案 0 :(得分：2)
我意识到这个问题的答案并不容易解释，但它与我试图通过命令字符串虚拟重建的列有关。我所做的以及解决问题的方法是在SELECT查询中放置要检索的特定列。
工作代码：
private void goDateBtn_Click(object sender, EventArgs e)
{
reportList.Items.Clear();
var db = new DBConnect();
MySqlCommand cmd = null;
MySqlDataReader dr = null;
double totalsales = 0;
try
{
if (db.OpenConnection() == true)
{
string cmdstr = "SELECT DISTINCT ol.*, o.order_ID, o.order_date, o.order_status, m.*, mc.menu_cost " +
"FROM orderlist ol " +
"INNER JOIN orderdb o ON ol.order_ID = o.order_ID " +
"INNER JOIN menudb m ON ol.menu_ID = m.menu_ID " +
"INNER JOIN " +
"(SELECT SUM(s.stock_pricePerPiece * r.recipe_quantity) AS menu_cost, m.menu_ID " +
"FROM recipelist r " +
"INNER JOIN stocksdb s ON r.stock_ID = s.stock_ID " +
"INNER JOIN menudb m ON r.menu_ID= m.menu_ID " +
"GROUP BY r.menu_ID " +
")" +
"mc ON m.menu_ID = mc.menu_ID " +
"WHERE o.order_date >= '" + fromDate.Value.Date.ToString("yyyy-MM-dd") + " 00:00:00" + "' AND " +
"o.order_date <= '" + toDate.Value.Date.ToString("yyyy-MM-dd") + " 23:59:59" + "' AND " +
"o.order_status = 'COMPLETED'";
if (menuCheckBox.Checked == true)
{
cmdstr = cmdstr + " AND m.menu_name = '" + menuBox.Text + "'";
}
cmd = new MySqlCommand(cmdstr, db.mycon);
dr = cmd.ExecuteReader();
string[] info = new string[20];
while (dr.Read())
{
info[1] = (dr["order_ID"].ToString());
info[2] = (dr["order_date"].ToString());
info[3] = (dr["menu_name"].ToString());
info[4] = (dr["order_quantity"].ToString());
info[5] = Convert.ToDouble(dr["menu_cost"].ToString()).ToString("#0.00");
info[6] = Convert.ToDouble(dr["menu_price"].ToString()).ToString("#0.00");
info[7] = ((Convert.ToDouble(dr["menu_price"].ToString()) * Convert.ToDouble(info[4])) - (Convert.ToDouble(dr["menu_cost"].ToString()) * Convert.ToDouble(info[4]))).ToString("#0.00");
this.reportList.Items.Add(new ListViewItem(new string[] { info[1], info[2], info[3], info[4], info[5], info[6], info[7] }));
totalsales += Convert.ToDouble(info[7]);
}
}
}
catch (MySqlException ex)
{
MessageBox.Show(ex.Message);
}
finally
{
if (dr != null)
{
dr.Close();
}
db.CloseConnnection();
}
totalSalesTxtBox.Text = totalsales.ToString("#0.00");
MessageBox.Show("SALES REPORT FINISHED!");
}
答案 1 :(得分：1)
完全根据您对问题的编辑消除我之前的答案，注意哪一行产生错误。
如果您执行以下操作会发生什么？它可能有助于诊断您的查询语法：
Console.WriteLine(cmdstr);
我注意到的一件事是你在括号后需要一个空格：
"GROUP BY stock_ID )"+
我不会认为会影响查询，但可能值得尝试。除此之外，我建议复制上面生成的查询并在您喜欢的SQL应用程序中手动粘贴它，并确保它在语法上是正确的。