using System;
using System.ComponentModel;
using System.Data;
using System.Windows.Forms;
namespace WindowsApplication1
{
    
public partial class Form1 : Form
    
{
        
        
public Form1()
        
...

       

        
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,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',1000,2000)";
            test 
= table.Select("id='id1'")[0]["exp1"];
            Console.WriteLine(test);
            
//test=1000;

            
//in运算符
            column.Expression = "iif(id not in('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(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)>0,0,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^&^
           
            
            
        }


        


    }

}