2

有两张桌子:

MyTable1:
  id       AutoNumber
  typecode Text

MyTable2
  id      AutoNumber
  pid     Number
  freq    Number

using System.Data.OleDb;
namespace AccessSelect
{
    class Program
    {
        static void Main(string[] args)
        {
            var sql = @"select 'x' from mytable1 where typecode=@typeCode and EXISTS (
                        select 'x' from mytable2 where (freq=0 OR freq=@freq) and mytable1.id=mytable2.pid)";

            using (OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=gpi.mdb;Jet OLEDB:Database Password=???"))
            {
                conn.Open();
                OleDbCommand cmd = new OleDbCommand(sql, conn);

                cmd.Parameters.Add(new OleDbParameter("@typeCode", "KK3000"));
                cmd.Parameters.Add(new OleDbParameter("@freq", 50));

                var o = cmd.ExecuteScalar();
            }
        }
    }
}

我不断收到异常“标准表达式中的数据类型不匹配”。

如果我更改 SQL 以包含值:

select 'x' from mytable1 where typecode='KK3000' and EXISTS (
 select 'x' from mytable2 where (freq=0 OR freq=50) and  mytable1.id=mytable2.pid)

我没有得到错误....

知道有什么问题吗?

4

2 回答 2

1

来自MSDN

当 CommandType 设置为 Text 时,OLE DB .NET 提供程序不支持将参数传递给 SQL 语句或由 OleDbCommand 调用的存储过程的命名参数。在这种情况下,必须使用问号 (?) 占位符。例如:

因此,将您的查询更改为:

select 'x' from mytable1 where typecode = ? 
     and EXISTS (select 'x' from mytable2 where (freq=0 OR freq = ?) and mytable1.id=mytable2.pid)

并且您必须以与查询中出现的顺序相同的顺序添加参数。

于 2013-07-18T05:44:42.647 回答
0

将其更改为:

static void Main(string[] args)
{
    var sql = @"select 'x' from mytable1 where typecode=@typeCode and EXISTS (
                select 'x' from mytable2 where (freq=0 OR freq=@freq) and mytable1.id=mytable2.pid)";

    using (OleDbConnection conn = new OleDbConnection(@"Provider=Microsoft.Jet.OLEDB.4.0;Data Source=gpi.mdb;Jet OLEDB:Database Password=???"))
    {
        conn.Open();
        OleDbCommand cmd = new OleDbCommand(sql, conn);

        cmd.Parameters.Add(new OleDbParameter("@freq", 50));
        cmd.Parameters.Add(new OleDbParameter("@typeCode", "KK3000"));

        var o = cmd.ExecuteScalar();
    }
}

现在它似乎工作了......虽然有点奇怪......

于 2013-07-18T07:28:29.847 回答