Question

public static DataTable LoadGrid(string SelectedItem,string yearSelected)

{

 DataTable tbl;

string a = SelectedItem;

string b = yearSelected;

string query =" SELECT top 10 SalesOrderID, RevisionNumber, OrderDate,DueDate, 
                            "ShipDate, Status,OnlineOrderFlag,SalesOrderNumber,PurchaseOrderNumber,AccountNumber, CustomerID, SalesPersonID, st.Name AS TerritoryName,BillToAddressID, ShipToAddressID,ShipMethodID, CreditCardID, CreditCardApprovalCode,CurrencyRateID, SubTotal, TaxAmt, Freight,TotalDue,Comment, soh.rowguid, soh.ModifiedDate FROM Sales.SalesOrderHeader soh INNER JOIN Sales.SalesTerritory st ON soh.TerritoryID = st.TerritoryID"+
WHERE  st.Name = "+a+"AND Datepart(year,OrderDate) = "+b;

tbl=DataAccess.cmd(query);
return (tbl);

}

传递给a的数据是一个区域，而b是b是从2个不同的下拉列表开始的年份，但是查询给出的错误是无效的列名加拿大（假设我从中选择加拿大下拉列表）和加拿大是名称列

中区域表中的表项

Answer 1

错误的原因是因为缺少引号。该查询是当前的 WHERE st.Name = Candada 虽然它应该是 WHERE st.Name = 'Canada' 代替。

请考虑使用存储过程，而不是使用内联SQL查询。

Answer 2

更具体地说，您应该使用以下语法

string query = string.Format(
            "SELECT top 10 SalesOrderID, RevisionNumber, OrderDate,"
           +" DueDate,ShipDate, Status,OnlineOrderFlag,SalesOrderNumber,"
        +"PurchaseOrderNumber,AccountNumber, CustomerID,SalesPersonID, st.Name AS TerritoryName,"
        +"BillToAddressID, ShipToAddressID,ShipMethodID,CreditCardID,"
        +"CreditCardApprovalCode,CurrencyRateID, SubTotal, TaxAmt, Freight,TotalDue,Comment,"
        +"soh.rowguid, soh.ModifiedDate FROM Sales.SalesOrderHeader soh "
        +"INNER JOIN Sales.SalesTerritory st ON soh.TerritoryID = st.TerritoryID "
       +" WHERE st.Name='{0}' AND Datepart(year,OrderDate) = '{1}'",a,b);

但在这些工作中使用sp ......：）

Answer 3

public static DataTable LoadGrid(string selectedItem,string yearSelected)
{
    DataTable tbl;
    string query = string.Format( @" SELECT top 10 SalesOrderID, RevisionNumber, OrderDate,DueDate,ShipDate, Status,OnlineOrderFlag,SalesOrderNumber,PurchaseOrderNumber,AccountNumber, CustomerID, SalesPersonID, st.Name AS TerritoryName,BillToAddressID, ShipToAddressID,ShipMethodID, CreditCardID, CreditCardApprovalCode,CurrencyRateID, SubTotal, TaxAmt, Freight,TotalDue,Comment, soh.rowguid, soh.ModifiedDate 
                FROM Sales.SalesOrderHeader as soh 
                INNER JOIN Sales.SalesTerritory as st 
                    ON soh.TerritoryID = st.TerritoryID
                WHERE  st.Name = '{0}' AND Datepart(year,OrderDate) = '{1}'", selectedItem, yearSelected);

    tbl=DataAccess.cmd(query);
    return (tbl);
}

这可以提高代码可读性，从而使编写查询更具可读性，并且不易出现语法错误。

Answer 4

SELECT top 10 SalesOrderID, RevisionNumber, OrderDate,DueDate, 
                            "ShipDate, Status,OnlineOrderFlag,SalesOrderNumber,PurchaseOrderNumber,AccountNumber, CustomerID, SalesPersonID, st.Name AS TerritoryName,BillToAddressID, ShipToAddressID,ShipMethodID, CreditCardID, CreditCardApprovalCode,CurrencyRateID, SubTotal, TaxAmt, Freight,TotalDue,Comment, soh.rowguid, soh.ModifiedDate FROM Sales.SalesOrderHeader soh INNER JOIN Sales.SalesTerritory st ON soh.TerritoryID = st.TerritoryID"+
WHERE  st.Name = "+a+"AND Datepart(year,OrderDate) = "+b;

为什么使用+运算符一次又一次地组合字符串，效率非常低且难以阅读，为什么不使用"{0}".format()?

需要帮助以下语法

4 个答案: