OlebExecuteScaler中的SELECT COUNT查询 [英] SELECT COUNT Query In OlebExecuteScaler

问题描述

大家好。



以下代码中哪一行错误：

  public   string  Sele_count_dont_pay_ghest（ string  U_today）
 {
  string  ret =  string  .Empty; 
  string  select_count_with_today =   SELECT COUNT（* ）FROM ghesting WHERE（date_ghest< =？）; 
 OleDbParameter [] pp =  new  OleDbParameter [ 1 ]; 
 pp [ 0 ] =  new  OleDbParameter（   date_ghest，OleDbType.Char）; 
 pp [ 0 ]。Value = Convert.ToString（U_today）; 
  //   a.Query_select_all_command（select_count_with_today）;  
 ret = a.Query_Select_ExecuteScaler （select_count_with_today）的ToString（）; 
 
  return  ret; 
 
} 

我有以下错误：

没有给出一个值或更多必需参数。



谢谢。

解决方案

您从未将参数添加到命令对象。



执行以下操作：

  string  select_count_with_today =   SELECT COUNT（*）FROM ghesting WHERE（date_ghest< =？）; 
 cmd.Parameters.AddWithValue（  @ date，U_today.ToString（）; 

使用.Parameters.AddWithValue（）意味着您可以在一行代码中添加参数，并且更容易阅读。

Hi all.

which line in the below code is wrong :

public string Sele_count_dont_pay_ghest(string U_today)
       {
           string ret = string.Empty;
           string select_count_with_today = "SELECT COUNT(*) FROM ghesting WHERE (date_ghest <= ? )";
           OleDbParameter[] pp = new OleDbParameter[1];
           pp[0] = new OleDbParameter("date_ghest", OleDbType.Char);
           pp[0].Value = Convert.ToString(U_today);
          // a.Query_select_all_command(select_count_with_today);
         ret =  a.Query_Select_ExecuteScaler(select_count_with_today).ToString();

         return ret;

       }

I have following error :
No value given for one or more required parameters.

thanks.

解决方案

You never added the parameter to the command Object.

Do something like this:

string select_count_with_today = "SELECT COUNT(*) FROM ghesting WHERE (date_ghest <= ? )";
cmd.Parameters.AddWithValue("@date", U_today.ToString();

using .Parameters.AddWithValue() means you can add the parameter in one line of code and is much easier to read.

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