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, EventArgs e)
... {
// 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.DataTable table = 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.DaTarow dRow = 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.DataColumn column = 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,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case when
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(id like '%1',2000) " ;
test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];
Console.WriteLine(test);
// test=1000;
// in运算符
column.Expression = " iif(id not in('id1'),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,iif(id like '%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
DataTable tableChild = new DataTable();
tableChild.Columns.Add( " id " , typeof ( string ));
tableChild.Columns.Add( " value " , typeof ( int ));
System.Data.DataSet ds = new DataSet();
ds.Tables.Add(tableChild);
ds.Tables.Add(table);
datarelation relation = new datarelation( " relation " , table.Columns[ " id " ], tableChild.Columns[ " id " ]);
ds.Relations.Add(relation);
for ( int i = 1 ; i <= 10 ; i ++ )
... {
System.Data.DaTarow dRow = 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);
// test=0.01818182;
// 计算父子表的差值,比如父表为库存数量，子表为订购数量，计算得出需要补充的数量
column.Expression = " iif(value-sum(child(relation).value)>0,value-sum(child(relation).value)) " ;
test = table.Select( " id='id1' " )[ 0 ][ " exp1 " ];
Console.WriteLine(test);
// test=-54;
// 比较遗憾的是没有发现能够计算同比和环比的方法，而且计算列无法作为约束
// ************结束，DataTable可以让你尽量发挥聪明才智来减少繁杂的sql语句并且减轻服务器计算符合^&^
}
}
}
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