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?