SQL 语句动态写法_ASP.NET

SQL 语句动态写法？在线等
SQL 语句能这样写吗我要查询的是动态的可变的

C# code

SqlConnection con = new SqlConnection("server=localhost;database=7daydian;uid=sa;pwd=1234");        string dia = "dianliang";        string sql = "select '"+dia+"' from tongji order by shijian";        SqlCommand com = new SqlCommand(sql, con);

我执行了下没有结果

应该怎样写啊
在线等急！

------解决方案--------------------------------------------------------
dia是字段名？
string sql = "select " + dia + " from tongji order by shijian";
这样写
------解决方案--------------------------------------------------------

C# code

 string sql = 'select "+dia+" from tongji order by shijian';
------解决方案--------------------------------------------------------
探讨

引用:
dia是字段名？
string sql = "select " + dia + " from tongji order by shijian";
这样写

C# code

string sql = "select distinct  [name] as 板块名称 ,[" + mon + "]as [周一]
,[" + thur + "]as [周2]
,[……

------解决方案--------------------------------------------------------
探讨

dia是字段名？
 string sql = "select " + dia + " from tongji order by shijian";
这样写