访问 SQL 查询缺少更多必需参数

Question

在一个网络项目中，我正在尝试执行以下查询：

SELECT ItemName as Name,
       ItemPicture as Picture,
       ItemHeroModif as Assistance,
       ItemTroopModif as Charisma,
       HerbCost as Herbs,
       GemCost as Gems
FROM Item WHERE ItemId = @value0

通过断点，我可以看到我附加到 @value0 的值 2。

尽管如此，我收到以下错误：

没有为一个或多个必需参数指定值。

我了解此错误通常是由于 SQL 语法错误而产生的。我的所作所为有什么问题吗？

编辑：

附件代码：

var madeForCommand = "SELECT ItemName as Name,ItemPicture as [Picture],ItemHeroModif as Assistance,ItemTroopModif as Charisma, HerbCost as Herbs, GemCost as Gems FROM Item WHERE ";
OleDbCommand command = new OleDbCommand();
for (int ii = 0; ii < items.Count; ii++)// items is a list of items with IDs I want to get from the query.
{
    madeForCommand += "ItemId =@value"+ii+" OR ";   
}
madeForCommand = madeForCommand.Substring(0, madeForCommand.Length - 4); // making sure I trim the final or; In the case I shown, it's just one item, so there are none at all.

后来：

OleDbCommand forOperations = new OleDbCommand(madeForCommand, _dbConnection); //_dbConnection is the connection to the database, it seems to work pretty well.
for (int ii = 0; ii < items.Count; ii++) 
{
    string attach = "@value" + ii;
    command.Parameters.AddWithValue(attach, items[ii].ID);
}

我很确定items[ii].ID 没问题，断点显示它等于 2 并且附件正常。

编辑 2： 我按照 Krish 和 Hans 的建议编辑了代码，我得到以下查询，没有任何附件：

SELECT ItemName as [Name],ItemPicture as Picture,ItemHeroModif as Assistance,ItemTroopModif as Charisma, HerbCost as Herbs, GemCost as Gems FROM [Item] WHERE (ItemID in (2));

如果有任何改变，我仍然会遇到同样的错误。

编辑 3： 在 Access 中执行查询要求我给参数“ItemPicture”一个值... ItemPicture 是一个列，不是吗？

Answer 1

Name、Item 和 Picture 在 Access 查询中是 problem words。将它们括在方括号中：

SELECT ItemName as [Name], ItemPicture as [Picture], ItemHeroModif as Assistance, ItemTroopModif as Charisma, HerbCost as Herbs, GemCost as Gems
FROM [Item] WHERE ItemID in (2);

由于将这些名称括起来仍然会给您一个缺少参数的投诉，因此我要求您在 Access 的查询设计器中测试该查询。在这种情况下，Access 提供了一个参数输入框，其中还包括 Access 解释为参数的单词。

您报告 Access 认为 ItemPicture 是一个参数。因此，通过在 Access Design View 中检查该表，您发现实际的字段名称是 ItemImageURL。

SELECT ItemName as [Name], ItemImageURL as [Picture], ItemHeroModif as Assistance, ItemTroopModif as Charisma, HerbCost as Herbs, GemCost as Gems
FROM [Item] WHERE ItemID in (2);

Answer 2

您没有从应用程序外部获取 Where 条件，因此字符串连接是安全的。 （至少我是这么认为的）

只需像这样添加参数：

var madeForCommand = "SELECT ItemName as Name,ItemPicture as Picture,ItemHeroModif as Assistance,ItemTroopModif as Charisma, HerbCost as Herbs, GemCost as Gems " +
    "FROM Item WHERE (ItemID in (";
     OleDbCommand command = new OleDbCommand();
     for (int ii = 0; ii < items.Count; ii++)// items is a list of items with IDs I want to get from the query.
     {
          if (i<=1) {
              madeForCommand += items[ii].ID
          }else {
              madeForCommand += "," + items[ii].ID;
          }
     }
    madeForCommand += "))"

最后你会得到一个类似的 SQL 查询：

"SELECT ItemName as Name,ItemPicture as Picture,ItemHeroModif as Assistance,ItemTroopModif as Charisma, HerbCost as Herbs, GemCost as Gems " +
"FROM Item WHERE (ItemID in (1,2,3))";

Answer 3

MS Access 不知道这样的参数：@value0!

请改用? 或named parameters，如下所示：

PARAMETERS [value0] INT;
SELECT ItemName as Name,
       ItemPicture as Picture,
       ItemHeroModif as Assistance,
       ItemTroopModif as Charisma,
       HerbCost as Herbs,
       GemCost as Gems
FROM Item WHERE ItemId = [value0];

如何调用这个查询？请阅读：Accessing Microsoft Office Data from .NET Applications
如需更多信息，请参阅：OleDbCommand.Parameters Property

[编辑]

据我了解，您希望将几个ItemId 传递到查询中。所以，你必须使用IN 子句：

SELECT ...
FROM ...
WHERE ItemID IN (1, 2, 5, 8)