如果存在查询则出错

问题描述

我在此代码中有错误我找不到它



此行中的错误4（字符串查询=如果存在（选择宠物的头像） Skey = @Skey）;）

I have error in this Code i can''t Find it

Error in this line 4 (string query = "if exists(select Avatar from pets Where Skey = @Skey);)

string connectionString = WebConfigurationManager.ConnectionStrings["conString"].ConnectionString;
SqlConnection con = new SqlConnection(connectionString);
string query = "if exists(select Avatar from pets  Where Skey = @Skey);
query += " begin select Avatar from pets  Where Skey = @Skey end";
query += " else  begin select Avatar from pets  Where Skey = '1' end" ;
SqlCommand cmd = new SqlCommand(query, con);
con.Open();
cmd.Parameters.AddWithValue("@Skey", Request.QueryString["ID"]);
object ReturnImage = cmd.ExecuteScalar();
byte[] photo = (byte[])ReturnImage;
Response.BinaryWrite(photo);
con.Close();

推荐答案

string connectionString = WebConfigurationManager.ConnectionStrings["conString"].ConnectionString;
          SqlConnection con = new SqlConnection(connectionString);
          string query = "if ((select COUNT(Avatar) from pets  Where Skey = @Skey)> 0)";
          query += " begin select Avatar from pets  Where Skey = @Skey end";
          query += " else  begin select Avatar from pets  Where Skey = '1' end" ;
          SqlCommand cmd = new SqlCommand(query, con);
          con.Open();
          cmd.Parameters.AddWithValue("@Skey", Request.QueryString["ID"]);
          object ReturnImage = cmd.ExecuteScalar();
          byte[] photo = (byte[])ReturnImage;
          Response.BinaryWrite(photo);
          con.Close();

还有一件事-----------



其中Skey =''1''结束;



应该是



其中Skey = 1结束;

And one more thing-----------

Where Skey = ''1'' end" ;

should be

Where Skey = 1 end" ;

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