System.Data.DataTable计算功能详解

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using System;

using System.ComponentModel;

using System.Data;

using System.Windows.Forms;

namespace WindowsApplication1

{

public partial class Form1:Form

{

public Form1()

{

InitializeComponent();

}

private void button1_Click( object sender,EventArgse)

{

// System.Data.DataTable计算功能详解，转载请保留以下信息

// 测试环境vs2005,c#

// 作者:jinjazz

// 作者blog: http://blog.csdn.net/jinjazz/

System.Data.DataTabletable = new DataTable();

// 计算常量，可以没有初始化列

object test = table.Compute( " 1+1 " , "" );

Console.WriteLine(test);

// test=2;

test = table.Compute( " 1+1 " , " false " );

Console.WriteLine(test);

// test=2;常数计算和filter无关

test = table.Compute( " abs(1) " , "" );

Console.WriteLine(test);

// test=null，不知道为这个什么没有抱错，而且返回null,其他的数学函数都会抱错

test = table.Compute( " 2%2 " , "" );

Console.WriteLine(test);

// test=0;

// 其他函数参考下面的计算列

// 初始化datatale

table.Columns.Add( " id " , typeof ( string ));

table.Columns.Add( " value " , typeof ( int ));

for ( int i = 1 ;i <= 10 ;i ++ )

{

System.Data.DataRowdRow = table.NewRow();

dRow[ " id " ] = " id " + i.ToString();

dRow[ " value " ] = i;

table.Rows.Add(dRow);

}

// test=table.Compute("value+1","true");

/// /抛出异常，这里必须是聚合函数

// *************************************支持的聚合函数********************** //

// 求数量

test = table.Compute( " count(id) " , " false " );

Console.WriteLine(test);

// test=0;

test = table.Compute( " count(id) " , " true " );

Console.WriteLine(test);

// test=10;

// 求和

test = table.Compute( " sum(value) " , "" );

Console.WriteLine(test);

// test=55;

// test=table.Compute("sum(id)","");

/// /抛出异常，这里不能是string

// 平均

test = table.Compute( " avg(value) " , "" );

Console.WriteLine(test);

// test=5;

// 最小

test = table.Compute( " min(value) " , "" );

Console.WriteLine(test);

// test=1;

// 最大

test = table.Compute( " max(value) " , "" );

Console.WriteLine(test);

// test=10;

// 统计标准偏差

test = table.Compute( " StDev(value) " , "" );

Console.WriteLine(test);

// test=3.02765035409749

// 统计方差

test = table.Compute( " Var(value) " , "" );

Console.WriteLine(test);

// test=9.16666666666667

// 复杂计算

test = table.Compute( " max(value)/sum(value) " , "" );

Console.WriteLine(test);

// test=0.181818181818182

/* ******************************************计算列************************ */

System.Data.DataColumncolumn = new DataColumn( " exp1 " , typeof ( float ));

table.Columns.Add(column);

// 简单计算

column.Expression = " value*2 " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=2;

// 字符串函数

column.Expression = " len(id) " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=3;

// 字符串函数

column.Expression = " len(''+id+'') " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=5;

// 字符串函数

column.Expression = " len(trim(''+id+'')) " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=3;

// 字符串函数

column.Expression = " substring(id,3,len(id)-2) " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=1; // substring的起始字符位置为1不是0

// 类型转换

column.Expression = " convert(substring(id,3,len(id)-2),'System.Int32')*1.6 " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=1.6;

// 相当于sqlserver的isnull

column.Expression = " isnull(value,10) " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=1;

// 三元运算符,相当于sqlserver的casewhen

column.Expression = " iif(value>5,1000,2000) " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=2000;

// like运算符

column.Expression = " iif(idlike'%1',1000,2000) " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=1000;

// in运算符

column.Expression = " iif(idnotin('id1'),1000,2000) " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=2000;

// 嵌套的三元运算

column.Expression = " iif(value>5,1000,iif(idlike'%1',4000,2000)) " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=4000;

// 客户端计算所占总数的百分比

column.Expression = " value/sum(value) " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=0.01818182

// 客户端计算差值,比如nba常规赛的胜场差

column.Expression = " max(value)-value " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=9

// ***********************父子表计算*************************************/

// 初始化子表,父子表关系

DataTabletableChild = new DataTable();

tableChild.Columns.Add( " id " , typeof ( string ));

tableChild.Columns.Add( " value " , typeof ( int ));

System.Data.DataSetds = new DataSet();

ds.Tables.Add(tableChild);

ds.Tables.Add(table);

DataRelationrelation = new DataRelation( " relation " ,table.Columns[ " id " ],tableChild.Columns[ " id " ]);

ds.Relations.Add(relation);

for ( int i = 1 ;i <= 10 ;i ++ )

{

System.Data.DataRowdRow = tableChild.NewRow();

dRow[ " id " ] = " id1 " ;

dRow[ " value " ] = i;

tableChild.Rows.Add(dRow);

}

// 计算子表记录数

column.Expression = " count(child(relation).value) " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// test=10;

// 计算父子表的百分比

column.Expression = " value/sum(child(relation).value) " ;

test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];

Console.WriteLine(test);

// <

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2008-04-08 22:11
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