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Everytime I run my program (f5 key) I get the error table chang9 already exists.. Does this mean that I will have to make a new sqlite table everytime I test my program??

I tried using the good ol' : DROP Table 'chang9'". But then I realized that after the program runs I cannot view the database table in the firefox viewer because it's been dropped.

How Do I avoid the table already exists error , while at the same time being able to view it after I'm done running my code?

 EDITED CODE with if not exists statement:

  // We use these three SQLite objects:
          SQLiteConnection sqlite_conn;
          SQLiteCommand sqlite_cmd;

          // create a new database connection: // Maybe error here - video was different
          sqlite_conn = new SQLiteConnection(@"Data Source=database.db;Version=3;");

          // open the connection:
          sqlite_conn.Open();

          // create a new SQL command:
          sqlite_cmd = sqlite_conn.CreateCommand();

          // Let the SQLiteCommand object know our SQL-Query:
          sqlite_cmd.CommandText = "CREATE TABLE IF NOT EXISTS 'tab1' (Seq text, Field text, Desc text, Len text, Dec text, Typ text, Percnt text, Pop text, Alzero text, MaxLen text );";

          // Now lets execute the SQL ;D                                                                                  
          sqlite_cmd.ExecuteNonQuery();

          sqlite_cmd.CommandText = "INSERT INTO tab1 (Seq, Field, Desc, Len, Dec, Typ, Percnt, Pop, Alzero, MaxLen) VALUES (@p1, @p2, @p3, @p4, @p5, @p6, @p7, @p8, @p9, @p10)";
          sqlite_cmd.Parameters.AddWithValue("@p1", 6);  // dummy initial values 
          sqlite_cmd.Parameters.AddWithValue("@p2", 878); 
          sqlite_cmd.Parameters.AddWithValue("@p3", 56);
          sqlite_cmd.Parameters.AddWithValue("@p4", 6);
          sqlite_cmd.Parameters.AddWithValue("@p5", 546);
          sqlite_cmd.Parameters.AddWithValue("@p6", 565);
          sqlite_cmd.Parameters.AddWithValue("@p7", 568);
          sqlite_cmd.Parameters.AddWithValue("@p8", 526);
          sqlite_cmd.Parameters.AddWithValue("@p9", 586);
          sqlite_cmd.Parameters.AddWithValue("@p10", 526);


          for (int i = 0; i < NumListValues; i += 10) // Filling SQlite table rows and columns with values from our list 
          {

              sqlite_cmd.Parameters.AddWithValue("@p1", list[i]);
              sqlite_cmd.Parameters.AddWithValue("@p2", list[i+1]);
              sqlite_cmd.Parameters.AddWithValue("@p3", list[i+2]);
              sqlite_cmd.Parameters.AddWithValue("@p4", list[i+3]);
              sqlite_cmd.Parameters.AddWithValue("@p5", list[i+4]);
              if (i > 490)
                  break; 
              sqlite_cmd.Parameters.AddWithValue("@p6", list[i+5]);
              sqlite_cmd.Parameters.AddWithValue("@p7", list[i+6]);
              sqlite_cmd.Parameters.AddWithValue("@p8", list[i+7]);
              sqlite_cmd.Parameters.AddWithValue("@p9", list[i+8]);
              sqlite_cmd.Parameters.AddWithValue("@p10", list[i+9]);
              sqlite_cmd.ExecuteNonQuery();

          }

       // sqlite_cmd.CommandText = " drop table if exists  'chan9'";


          sqlite_conn.Close();
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2 回答 2

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只有当它不存在时，您才可以使用“CREATE TABE chang9 ... IF NOT EXISTS”来创建它。

然后如果你想清空它，你可以在再次填充之前“从 chang9 中删除”。

于 2013-11-04T14:35:41.880 回答
2

您可以在创建之前删除表，而不是在处理结束时。

这样，您的表及其数据在您运行 rcode 后可用，并且每次运行时您仍会获得一个新表。

于 2013-11-04T14:37:29.113 回答