参数化查询速度慢的原因及分析

测试环境：sql2005 + .NET2.0

同样的SQL语句，参数化查询和SQL语句直接执行的速度对比。数据库中存放的字段类型是varchar

注：不建议使用SQL拼接的方式。因为会造成SQL注入的危险。 

结论：

1.对参数要设置正确的　　DbType(varchar = AnsiString, nvarchar=String,char=AnsiStringFixedLength,nchar=StringFixedLength)

2.尽量使用数据库类型对应的DbType的。

3.尽量给参数的size设置大小

Code:

class Program
    {
        private delegate void Action();

        static void Main(string[] args)
        {
            while (true)
            {
                ExecuteDataSetWithParam(false);
                ExecuteDataSetWithParam(true);
                ExecuteDataSetWithParamAnsiString(false);
                ExecuteDataSetWithParamAnsiString(true);
                ExecuteDataSetWithParamSqlDbType(false);
                ExecuteDataSetWithParamSqlDbType(true);

                ExecuteDataSetNoneParam();
                Console.ReadLine();
            }

        }

        private static void ExecuteDataSetWithParam(bool len)
        {
            #region Sql
            string sql = @"";
            #endregion
            List<IDataParameter> paras = new List<IDataParameter>();

            paras.Add(new System.Data.SqlClient.SqlParameter("@Deleted", DbType.String) { Value = "0" });
            if (len)
                foreach (SqlParameter v in paras)
                {
                    v.Size = v.Value.ToString().Length;
                }
            Invoke(delegate { ExecuteDataSet(sql, paras); }, "参数化查询" + (len ? " 指定长度" : string.Empty));
        }

        private static void ExecuteDataSetWithParamAnsiString(bool len)
        {
            #region Sql
            string sql = @"";
            #endregion
            List<IDataParameter> paras = new List<IDataParameter>();


            paras.Add(new System.Data.SqlClient.SqlParameter("@Deleted", DbType.AnsiString) { Value = "0" });
            if (len)
                foreach (SqlParameter v in paras)
                {
                    v.Size = v.Value.ToString().Length;
                }
            Invoke(delegate { ExecuteDataSet(sql, paras); }, "参数化查询AnsiString" + (len ? " 指定长度" : string.Empty));
        }
        private static void ExecuteDataSetWithParamSqlDbType(bool len)
        {
            #region Sql
            string sql = @"";
            #endregion
            List<IDataParameter> paras = new List<IDataParameter>();

            paras.Add(new System.Data.SqlClient.SqlParameter("@Deleted", SqlDbType.VarChar) { Value = "0" });
            if (len)
                foreach (SqlParameter v in paras)
                {
                    v.Size = v.Value.ToString().Length;
                }
            Invoke(delegate { ExecuteDataSet(sql, paras); }, "参数化查询SqlDbType" + (len ? " 指定长度" : string.Empty));
        }

        private const string dbConnStr = "";
        private static void ExecuteDataSetNoneParam()
        {
            #region Sql
            string sql = @"' 
Order By
     RegisterDate desc";
            #endregion
            Invoke(delegate { ExecuteDataSet(sql, null); }, "SQL语句拼接");
        }

        private static void Invoke(Action action, string name)
        {
            try
            {
                var star = DateTime.Now;
                action.Invoke();
                var time = DateTime.Now - star;
                Console.WriteLine(name + " - TimeLost:" + time.ToString());
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
            }
        }

        private static void ExecuteDataSet(string sql, List<IDataParameter> AParas)
        {
            using (IDbConnection conn = new SqlConnection(dbConnStr))
            {
                using (System.Data.IDbCommand cmd = new SqlCommand(sql))
                {
                    cmd.Connection = conn;
                    AddParam(cmd, AParas);

                    System.Data.IDbDataAdapter adapt = new SqlDataAdapter(cmd as SqlCommand);

                    var ds = new DataSet();
                    adapt.Fill(ds);
                }
            }
        }

        private static void AddParam(IDbCommand cmd, List<IDataParameter> AParas)
        {
            if (AParas == null) return;
            foreach (var v in AParas)
            {
                cmd.Parameters.Add(v);
            }
        }
    }