Question

我正在尝试检查数据库中是否已存在某些ID。如果没有，我希望用户将id更改为其他内容。

所有这一切都在textobx的TextChanged函数中完成。

问题是我收到错误，因为查询看起来不错，我不确定为什么我会看到这个：The SELECT statement includes a reserved word or an argument name that is misspelled or missing, or the punctuation is incorrect.

进行检查的方法：

private bool DoesIDExist(int dataID, string filePath)
{
    HashPhrase hash = new HashPhrase();
    DataTable temp = new DataTable();

    string hashShortPass = hash.ShortHash(pass);
    bool result = false;

    // Creating a connection string. Using placeholders make code
    // easier to understand.
    string connectionString =
        @"Provider=Microsoft.ACE.OLEDB.12.0; Data Source={0};
          Persist Security Info=False; Jet OLEDB:Database Password={1};";

    string sql = string.Format
        ("SELECT FROM PersonalData WHERE [DataID] = {0}", dataID);

    using (OleDbConnection connection = new OleDbConnection())
    {
        // Creating command object.
        // Using a string formatting let me to insert data into
        // place holders I have used earlier.
        connection.ConnectionString =
            string.Format(connectionString, filePath, hashShortPass);

        using (OleDbCommand command = new OleDbCommand(sql, connection))
        {
            // Creating command object.
            // Using a string formatting let me to insert data into
            // place holders I have used earlier.
            connection.ConnectionString =
                string.Format(connectionString, filePath, hashShortPass);

            try
            {
                // Open database connection.
                connection.Open();

                using (OleDbDataReader read = command.ExecuteReader())
                {
                    // Checking if there is any data in the file.
                    if (read.HasRows)
                    {
                        // Reading information from the file.
                        while (read.Read())
                        {
                            if (read.GetInt32(0) == dataID)
                                return true;
                        }
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show("Error: " + ex.Message);
            }
        }
    }

    return result;
}

Answer 1

我认为你的选择缺少一些你想要提取的列？

string sql = string.Format
    ("SELECT FROM PersonalData WHERE [DataID] = {0}", dataID);

不应该是这样的：

string sql = string.Format
    ("SELECT * FROM PersonalData WHERE [DataID] = {0}", dataID);

Answer 2

您需要在SELECT子句中指定一些内容。我想：

SELECT DataID FROM PersonalData WHERE ...

Answer 3

你错过了选择的内容

string sql = string.Format
    ("SELECT FROM PersonalData WHERE [DataID] = {0}", dataID);

更改为

string sql = string.Format
    ("SELECT * FROM PersonalData WHERE [DataID] = {0}", dataID);

并且：您可以像构建查询一样对SQL-Injection开放。

Answer 4

问题在于这行代码：

string sql = string.Format
        ("SELECT FROM PersonalData WHERE [DataID] = {0}", dataID);

您需要指定要选择的内容。示例：SELECT *，SELECT [MyColumn]，SELECT TOP 1 *等。根据您的要求，您可能会找到类似的内容：

string sql = string.Format
 ("SELECT COUNT(*) AS UserCount FROM PersonalData WHERE [DataID] = {0}", dataID);

其他信息：

如果在网络上使用此方法，比如从查询字符串中提取ID，那么您将自己打开 SQL注入攻击。略微修改代码可以解决问题：

string sql = "SELECT FROM PersonalData WHERE [DataID] = @DataID";

using (OleDbCommand command = new OleDbCommand(sql, connection))
        {
            command.Parameters.AddWithValue("@DataID", dataID);
        }

检查数据库文件中是否存在ID时出错

4 个答案: