如果C#中存在表，则删除该表吗? [英] Drop a table if it exists in C#?

问题描述

我只想使用MySql在C#中删除表(如果存在).

I want to drop a table only if it exists , in C# with MySql .

考虑以下代码:

namespace CSharpMySqlSample
{
   class Example2
   {
      static void Main()
      {
         String str = @"server=localhost; database=sakila; uid=root;                password=root;";
         MySqlConnection con = null;
         try
         {
            con = new MySqlConnection(str);
            con.Open(); //open the connection        
            String cmdText = @"drop table `sakila`.`testable` if exists"; // this one drops a table 
            MySqlCommand cmd = new MySqlCommand(cmdText, con);
            cmd.Prepare();
            cmd.ExecuteNonQuery(); //execute the mysql command
         }
         catch (MySqlException err)
         {
            String outp = err.ToString();
            Console.WriteLine("Error: " + err.ToString());
         }
         finally
         {
            if (con != null)
            {
               con.Close(); //close the connection
            }
         } //remember to close the connection after accessing the database
      }
   }
}

它产生了:

"MySql.Data.MySqlClient.MySqlException:您的SQL错误 句法;检查与您的MySQL服务器版本相对应的手册 在第1行\ r \ n处的如果存在"附近使用正确的语法 MySql.Data.MySqlClient.MySqlStream.ReadPacket()\ r \ n在 MySql.Data.MySqlClient.NativeDriver.GetResult(Int32& Row， Int64& insertId)\ r \ n位于 MySql.Data.MySqlClient.Driver.GetResult(Int32 statementId，Int32& 受影响的行，Int64& insertId)\ r \ n位于 MySql.Data.MySqlClient.Driver.NextResult(Int32 statementId，Boolean 力)\ r \ n at MySql.Data.MySqlClient.MySqlDataReader.NextResult()\ r \ n在 MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior 行为)\ r \ n MySql.Data.MySqlClient.MySqlCommand.ExecuteReader()\ r \ n在 MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery()\ r \ n在 CSharpMySqlSample.Example2.Main()

"MySql.Data.MySqlClient.MySqlException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'if exists' at line 1\r\n at MySql.Data.MySqlClient.MySqlStream.ReadPacket()\r\n at MySql.Data.MySqlClient.NativeDriver.GetResult(Int32& affectedRow, Int64& insertedId)\r\n at MySql.Data.MySqlClient.Driver.GetResult(Int32 statementId, Int32& affectedRows, Int64& insertedId)\r\n at MySql.Data.MySqlClient.Driver.NextResult(Int32 statementId, Boolean force)\r\n at MySql.Data.MySqlClient.MySqlDataReader.NextResult()\r\n at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader(CommandBehavior behavior)\r\n at MySql.Data.MySqlClient.MySqlCommand.ExecuteReader()\r\n at MySql.Data.MySqlClient.MySqlCommand.ExecuteNonQuery()\r\n at CSharpMySqlSample.Example2.Main()

那么查询出了什么问题?

So what's wrong with the query ?

推荐答案

尝试一下:

DROP TABLE IF EXISTS sakila.testtable;

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