如何在不考慮是否在C＃Windows窗體中傳遞參數的情況下創建動態SQL查詢以運行

Question

我正在使用VS 2012和SQL Express

我正在嘗試構建Windows窗體應用程序以通過C＃數據庫進行搜索，它在窗體上具有不同的控件，這些控件作為參數傳遞給查詢。

查詢中的參數不一定要傳遞幾次

我正在嘗試以下代碼示例。

SELECT a.ID AS 'DealID', a.TradeDate, c.COMPANYNAME AS 'Seller Company', 
       a.SellCommission, h.BROKER_FULLNAME AS 'Seller Trader', 
       j.DisplayName AS 'Seller Broker', d.COMPANYNAME AS 'Buyer Company', 
       a.BuyCommission, g.BROKER_FULLNAME AS 'Buyer Trader', 
       i.DisplayName AS 'Buyer Broker', e.PRODUCT_NAME, f.TYPE_DESC AS 'Quantity Type',
       f.NBR_OF_GALLONS AS 'Quantity Multiplier', a.ContractVolume, a.TotalVolume, 
       a.DeliveryPoint, a.Price, a.ContractStart, a.ContractEnd
FROM Confirmations AS a WITH (nolock) 
LEFT OUTER JOIN COMPANY AS c WITH (nolock) 
  ON c.COMPANY_ID = a.SellCompany
LEFT OUTER JOIN COMPANY AS d WITH (nolock) 
  ON d.COMPANY_ID = a.BuyCompany 
LEFT OUTER JOIN BIOPRODUCTTYPES AS e WITH (nolock) 
  ON e.ID = a.ProductID 
LEFT OUTER JOIN BIO_QUANTITY_TYPE AS f WITH (nolock) 
  ON f.ID = a.QuantityTypeID 
LEFT OUTER JOIN COMPANYBROKER AS g WITH (nolock) 
  ON g.COMPANYBROKER_ID = a.BuyTrader 
LEFT OUTER JOIN COMPANYBROKER AS h WITH (nolock) 
  ON h.COMPANYBROKER_ID = a.SellTrader 
LEFT OUTER JOIN Users AS i WITH (nolock) 
  ON i.ID = a.BuyBroker 
LEFT OUTER JOIN Users AS j WITH (nolock) 
  ON j.ID = a.SellBroker
WHERE (@fromdate IS NULL OR @fromdate=' ' OR a.TradeDate >= @fromdate) 
       AND (@todate IS NULL OR @todate=' ' OR a.TradeDate <= @todate) 
       AND (@buycompanyname IS NULL 
            OR @buycompanyname="" 
            OR a.BuyCompany = (SELECT COMPANY_ID
                               FROM COMPANY
                               WHERE (COMPANYNAME = @buycompanyname)))              
       AND (@sellcompanyname IS NULL 
            OR @sellcompanyname="" 
            OR a.SellCompany = (SELECT COMPANY_ID
                                FROM COMPANY
                                WHERE (COMPANYNAME =@sellcompanyname))) 
       AND (@product IS NULL OR @product="" OR e.PRODUCT_NAME= @product)";

我可以使用傳遞的參數而不是上面的查詢來動態創建查詢，這似乎更合乎邏輯，因為如果表中的列具有空值，則不查找記錄。

Answer 1

這就是ORM創建的目的。 通過用在運行時構建查詢的東西（例如Entity Framework或NHibernate ）替換硬編碼的查詢，並為您構建查詢的SELECT和WHERE部分。

通過正確設置對象，您可以使用如下所示的實體框架

Nullable<DateTime> fromDate = //...
Nullable<DateTime> toDate = //...
string buyCompany = //...

//(Snip)

using(var ctx = new MyContext())
{
    var query = ctx.Order;

    if(fromDate.HasValue)
        query = query.Where(ent=> ent.TradeDate >= fromDate.Value);
    if(toDate.HasValue)
        query = query.Where(ent => ent.TradeDate <= toDate.Value);
    if(String.IsNullOrWhitespace(buyCompany) == false)
        query = query.Where(ent => ent.BuyCompany.CompanyName = buyCompany);

    //(Snip)

    return query.ToList();
}

Answer 2

是的，只需構建您的sql查詢字符串即可。

將您的SqlCommand.CommandType設置為CommandType.Text然后使用SqlCommand.Parameters.AddWidthValue(string, object);設置參數SqlCommand.Parameters.AddWidthValue(string, object);

Answer 3

如果要調用存儲過程，建議您動態構建SQL字符串以僅使用將要使用的參數，然后調用sp_executesql。 存儲過程如下所示：

DECLARE @sql =nvarchar(MAX), @Parameters nvarchar(max)
SET @sql = 'SELECT * FROM [dbo].[Foo] WHERE Column1 = @Param1'
SET @Parameters = '@Param1 nvarchar(32), @Param2 nvarchar(32)'
IF(@Param2 is not null and @Param2 <> ' ') SET @sql = @sql + ' AND Column2 = @Param2'
EXEC sp_executesql @Sql, @Parameters, @Param1, @Param2

如果您使用C＃而不是存儲過程來構建查詢字符串，則想法基本相同：

command.CommandText = "SELECT * FROM [dbo].[Foo] WHERE Column1 = @Param1";
command.Parameters.AddWithValue("@Param1", param1);
if(!String.IsNullOrEmpty(param2))
{
    command.CommandText += " AND Column2 = @Param2";
    command.Parameters.AddWithValue("@Param2", param2);
}