System.Data.DataTable计算功能详解
发布时间：2020-12-12 15:56:07 所属栏目：MsSql教程 来源：网络整理
导读：? 转帖： using ?System; using ?System.ComponentModel; using ?System.Data; using ?System.Windows.Forms; namespace ?WindowsApplication1 { ???? public ? partial ? class ?Form1?:?Form ????{ ???????? ???????? public ?Form1() ????????{ ?????????
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? 转帖： 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^&^ ???????????????????????????????????????????}????????????}} ? （编辑：李大同） 【声明】本站内容均来自网络，其相关言论仅代表作者个人观点，不代表本站立场。若无意侵犯到您的权利，请及时与联系站长删除相关内容! |