Question

当我尝试通过ID查找时，我一直收到此错误：

system.data.oledb.oledbexception指定字段“ ID”可以引用到SQL语句的FROM子句中列出的多个表

这是我的代码：

public static Invoice GetInvoice(string id)
    {
        OleDbConnection conn = GetConnection();
        Invoice invoice = null;
        if (conn == null)
        {
            return null;
        }
        string sqlString = "SELECT * FROM Person INNER JOIN Employee ON " +
            "Person.ID=Employee.ID WHERE ID = @ID";
        OleDbCommand comm = new OleDbCommand(sqlString, conn);
        comm.Parameters.AddWithValue("@ID", id);
        OleDbDataReader dr = null;
        try
        {
            conn.Open();
            dr = comm.ExecuteReader(CommandBehavior.SingleRow);
            if (dr.Read())
            {
                invoice = new Invoice();
                invoice.PersonID = (string)dr["ID"];
                invoice.FirstName = (string)dr["FirstName"];
                invoice.LastName = (string)dr["LastName"];
                invoice.Age = (int)dr["Age"];
            }
        }
        catch (Exception ex)
        {
            invoice = null;
            MessageBox.Show(ex.ToString());
        }
        finally
        {
            if (conn.State == ConnectionState.Open)
            {
                conn.Close();
            }
        }
        return invoice;
    }

Answer 1

您需要更改查询，在选择通配符'*'时，这意味着它会同时提取人员ID和员工ID，但没有唯一的引用。更改通配符以提取确切的表ID，如下所示：

SELECT Person.ID, FirstName, LastName FROM...

您还需要将WHERE语句更改为以下内容：

WHERE Person.ID = @ID

因为where语句不知道要过滤哪个表ID（我知道它们是相同的值，但是SQL对此并不关心）

指定的字段“ ID”可以引用多个表

1 个答案: