简单的参数化 select 查询需要时间在 C# 中执行

Question

我有一个 table 结构，如下所示：

CREATE TABLE [dbo].[MainTbl](
[RowNum] [int] IDENTITY(1,1) NOT NULL,
[TxtID] [varchar](20) NOT NULL,
[TxtKey] [varchar](20) NOT NULL,
[TrnDate] [datetime] NOT NULL,
[SrcID] [varchar](20) NOT NULL DEFAULT (''),
[ElemName] [varchar](20) NOT NULL,
[TblXml] [varchar](max) NOT NULL,
[ActiveStatus] [varchar](20) NOT NULL DEFAULT (''),
[DevLvl] [int] NOT NULL DEFAULT ((0)),
[Archive] [bit] NULL CONSTRAINT [DF_MainTbl_Archive]  DEFAULT ((0)),

CONSTRAINT [pkMainTbl] PRIMARY KEY CLUSTERED 
([RowNum] ASC)
WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF,
ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]) ON [PRIMARY] TEXTIMAGE_ON [PRIMARY]

并执行以下查询以获取 xml :

select TblXml from MainTbl with (nolock) 
where TrnDate < @TrnDate and TxtID = @TxtID and TxtKey = @TxtKey 
and ActiveStatus != 'NonActive' and ElemName = 'xyz' order by TrnDate desc

此查询在 SSMS 中的执行时间为 5 秒，但通过 C# 代码执行时，大约需要 5 分钟以上。

我的 C# 代码接受查询案例号。在 "BuildQuery" 中准备上述语句和 return一个sqlcommand，我传参执行，但是"sqlCommand.ExecuteReader();"耗时多

private bool MainFunction(parameters)
{
    CheckXMLDate(4,'9/6/2016 1:00:00 PM','ABC','123' );
}

________________________________

public bool CheckXMLDate(bldqry,TrnDate,TxtID,TxtKey )
{
    SqlCommand sqlCommand = BuildQuery(bldqry);

    sqlCommand.Parameters.AddWithValue("@TrnDate", TrnDate);
    sqlCommand.Parameters.AddWithValue("@TxtID", TxtID);
    sqlCommand.Parameters.AddWithValue("@TxtKey", TxtKey);
    SqlDataReader dataReader = sqlCommand.ExecuteReader();

    //Some statements like below...
    if (check == success)
   {    dataReader.Close();
        return true;}

    dataReader.Close();
    return false;
}
_______________________________________

public SqlCommand BuildQuery(int caseNum)
{
string QryString = string.Empty;
SqlCommand sqlCommand = new SqlCommand(); 
sqlCommand.CommandType = CommandType.Text;
sqlCommand.Connection = con;

switch (caseNum)
{                
case 4: 
        {
            QryString = "select TblXml from MainTbl with (nolock) "+
                        "where TrnDate < @TrnDate "+
                        "and TxtID = @TxtID "+
                        "and TxtKey = @TxtKey " +
                        "and ActiveStatus != 'NonActive' and ElemName = 'xyz' order by TrnDate desc";
            break;
        }
 default:
        { break; }
}
sqlCommand.CommandText = QryString;
sqlCommand.CommandTimeout = 800;
return sqlCommand;
}

此处参数均为字符串类型

Answer 1

您似乎没有任何索引来优化查询。在 (ElemName, TxtID, TxtKey, ActiveStatus, TrnDate)

上创建多字段索引

Answer 2

传递参数时的以下更改提高了查询的性能，并且它在几秒钟内再次执行。

sqlCommand.Parameters.Add("@TrnDate", SqlDbType.VarChar).Value = TrnDate;
sqlCommand.Parameters.Add("@TxtID", SqlDbType.VarChar).Value = TxtID;
sqlCommand.Parameters.Add("@TxtKey", SqlDbType.VarChar).Value = TxtKey;

感谢大家的建议！

简单的参数化 select 查询需要时间在 C# 中执行

Simple parameterized select query takes time to execute in C#

c#

sql

ssms