SqlServer怎樣獲取查詢(xún)語(yǔ)句的成本

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在有些大系統(tǒng)中,客戶(hù)端查詢(xún)非常復(fù)雜,需要顯示很多字段和過(guò)濾很多條件,例如TFS中的條件過(guò)濾,或則用戶(hù)希望客戶(hù)端查詢(xún)能像EXCEL過(guò)濾那樣方便

這樣可能導(dǎo)致查詢(xún)語(yǔ)句非常復(fù)雜,此時(shí)的效率也比較低.

TFS查詢(xún)條件界面:

如果可以獲取查詢(xún)語(yǔ)句的成本,當(dāng)SQL語(yǔ)句執(zhí)行成本很大(可能執(zhí)行時(shí)間會(huì)很長(zhǎng)時(shí)),系統(tǒng)自動(dòng)提示用戶(hù)是否繼續(xù)或則大概需要多長(zhǎng)時(shí)間,這樣會(huì)提高用戶(hù)體驗(yàn).

下舉一例:

查詢(xún)Sql Server中的所有列信息表:sys.all_columns

在Sql server 2k8 management studio 中先后執(zhí)行下面每行語(yǔ)句即可得到Sql語(yǔ)句的成本, 即為第二個(gè)語(yǔ)句執(zhí)行結(jié)果中第一行中TotalSubtreeCost字段值.

set showplan_all on
select * from sys.all_columns

第二個(gè)語(yǔ)句(select * from sys.all_columns)執(zhí)行結(jié)果:

再執(zhí)行 set showplan_all off結(jié)束查詢(xún)計(jì)劃分析結(jié)果.

此時(shí)可以應(yīng)用showplan_all來(lái)獲取Sql查詢(xún)的成本.

如下為C#簡(jiǎn)單實(shí)現(xiàn)上述應(yīng)用,在VS2k8中編譯通過(guò),只需正確更改Data Source即可運(yùn)行:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Data.SqlClient;
using System.Data;
using System.Diagnostics;

namespace ConsoleApplication1
{
class Program
{
static void Main(string[] args)
{
SqlConnectionStringBuilder connectionBuilder = new SqlConnectionStringBuilder();
connectionBuilder.Add("Data Source", "your server name or ip");
connectionBuilder.Add("Initial Catalog", "master");
connectionBuilder.Add("Integrated Security", "True");

string sqlStr = "select * from sys.all_columns";
Console.WriteLine(GetSqlCost(connectionBuilder.ToString(), sqlStr).ToString());
Console.Read();
}

static double GetSqlCost(string connectStr, string strSQL)
{
double sqlCost;
int timeOut;
SqlDataAdapter adapter;
SqlConnection connection = new SqlConnection(connectStr);
SqlCommand command;
DataTable table;
timeOut = 180;
adapter = null;

try
{
connection.Open();
command = new SqlCommand("set showplan_all on ", connection);
command.ExecuteNonQuery();
command.CommandText = strSQL;
adapter = new SqlDataAdapter(strSQL, connection);
adapter.SelectCommand.CommandTimeout = timeOut;
table = new DataTable();
adapter.Fill(table);
command.CommandText = "set showplan_all off";
command.ExecuteNonQuery();
sqlCost = System.Convert.ToDouble(table.Rows[0]["TotalSubtreeCost"]);
}
finally
{
command = null;
connection.Close();
}
return sqlCost;
}
}

}