查询结果始终为空。 [英] Query result is always empty.

问题描述

你好。我无法从数据库中读取数据。查询结果为空。我关注这篇文章： GUIDE 。此外，直接在DB中执行查询返回我希望的结果。 DB是SQLSERVER 2012.我做错了什么？

 ...  string  search ....  //  函数的参数 
 
 SqlParameter sqlp =  new  SqlParameter（  @ searchSome ，System.Data.SqlDbType.NVarChar，search.Length）; 
 sqlp.Value = search; 
 
 SqlCommand cmd =  new  SqlCommand（  SELECT EngLyrics FROM dbo.Lyrics WHERE SongName LIKE'％@ searchSome％';，DBConnectInfo.connection）; 
 cmd.Parameters.Add（sqlp）; 
 
 尝试 
 {
 使用（SqlDataReader sdr = cmd.ExecuteReader（））
 {
  string  result =  String  .Empty ; 
  while （sdr.Read（））
 {
 result = sdr [   EngLyrics]。ToString（）; 
 返回结果; 
} 
 返回结果; 
} 
} 
  catch （SqlException ex）{ return  ex的ToString（）; } 
  finally  
 {
 DBConnectInfo.connection.Close（）; 
} 

解决方案

'％@ searchSome％'是一个字符串，因此SQL不会尝试进行参数替换。

尝试：

 SqlCommand（  SELECT EngLyrics FROM dbo.Lyrics WHERE SongName LIKE'％'+ @ searchSome +'％';，DBConnectInfo.connection）; 

Hi there. I cannot read my data from database. The query result is empty. I following to this article: GUIDE. Also, executing queries directly in DB returns me wished results. DB is SQLSERVER 2012. What i did wrong?

...string search....//the function's argument

SqlParameter sqlp = new SqlParameter("@searchSome", System.Data.SqlDbType.NVarChar, search.Length);
                    sqlp.Value = search;

                    SqlCommand cmd = new SqlCommand("SELECT EngLyrics FROM dbo.Lyrics WHERE SongName LIKE '%@searchSome%';", DBConnectInfo.connection);
                    cmd.Parameters.Add(sqlp);
                    
                    try
                    {
                        using (SqlDataReader sdr = cmd.ExecuteReader())
                        {
                            string result = String.Empty;
                            while (sdr.Read())
                            {
                                result = sdr["EngLyrics"].ToString();
                                return result;
                            }
                            return result;
                        }
                    }
                    catch (SqlException ex) { return ex.ToString(); }
                    finally
                    {
                        DBConnectInfo.connection.Close();
                    }

解决方案

'%@searchSome%' Is a string, so SQL does not try to do and parameter substitution.
Try:

SqlCommand("SELECT EngLyrics FROM dbo.Lyrics WHERE SongName LIKE '%' + @searchSome + '%';", DBConnectInfo.connection);

这篇关于查询结果始终为空。的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！