C#中DataTable中的Compute方法使用收集

  1         DataTable dt = new DataTable();
  2         //嵌套的三元運算 牛叉到五體投地
  3         object obj = dt.Compute("iif(1000=5,1000,iif(100>100,4001,2000))", null);
  4         Response.Write(obj);
  5 
  6 
  7         System.Data.DataTable table = new DataTable();
  8         //計算常量，能夠沒有初始化列
  9         object test = table.Compute("1+1", "");
 10         Console.WriteLine(test);
 11 
 12         string a = "123";
 13         System.Double b = 123;
 14         decimal c = 123m;
 15         Console.WriteLine(Convert.ToDecimal(a));
 16         //test=2;
 17 
 18         test = table.Compute("1+1", "false");
 19         Console.WriteLine(test);
 20         //test=2;常數計算和filter無關
 21 
 22         test = table.Compute("abs(1)", "");
 23         Console.WriteLine(test);
 24         //test=null，不知道爲這個什麼沒有報錯，並且返回null,其餘的數學函數都會抱錯
 25 
 26         test = table.Compute("2%2", "");
 27         Console.WriteLine(test);
 28         //test=0;
 29         //其餘函數參考下面的計算列
 30 
 31 
 32 
 33         //初始化datatale
 34         table.Columns.Add("id", typeof(string));
 35         table.Columns.Add("value", typeof(int));
 36         for (int i = 1; i <= 10; i++)
 37         {
 38             System.Data.DataRow dRow = table.NewRow();
 39             dRow["id"] = "id" + i.ToString();
 40             dRow["value"] = i;
 41             table.Rows.Add(dRow);
 42         }
 43 
 44 
 45 
 46         //test = table.Compute("value+1", "true");
 47         /**/
 48         ////拋出異常，這裏必須是聚合函數
 49 
 50 
 51 
 52         //*************************************支持的聚合函數**********************//
 53 
 54         //求數量
 55         test = table.Compute("count(id)", "false");
 56         Console.WriteLine(test);
 57         //test=0;
 58 
 59         test = table.Compute("count(id)", "true");
 60         Console.WriteLine(test);
 61         //test=10;
 62 
 63 
 64 
 65         //求和
 66         test = table.Compute("sum(value)", "");
 67         Console.WriteLine(test);
 68         //test=55;
 69 
 70         //test = table.Compute("sum(id)","");
 71         /**/
 72         ////拋出異常，這裏不能是string
 73 
 74 
 75         //平均
 76         test = table.Compute("avg(value)", "");
 77         Console.WriteLine(test);
 78         //test=5;
 79 
 80 
 81         //最小
 82         test = table.Compute("min(value)", "");
 83         Console.WriteLine(test);
 84         //test=1;
 85 
 86         //最大
 87         test = table.Compute("max(value)", "");
 88         Console.WriteLine(test);
 89         //test=10;
 90 
 91         //統計標準誤差
 92         test = table.Compute("StDev(value)", "");
 93         Console.WriteLine(test);
 94         //test=3.02765035409749
 95 
 96         //統計方差
 97         test = table.Compute("Var(value)", "");
 98         Console.WriteLine(test);
 99         //test=9.16666666666667
100 
101 
102         //複雜計算
103         test = table.Compute("max(value)/sum(value)", "");
104         Console.WriteLine(test);
105         //test=0.181818181818182
106 
107         /**/
108         /*******************************************計算列*************************/
109 
110         System.Data.DataColumn column = new DataColumn("exp1", typeof(float));
111         table.Columns.Add(column);
112 
113 
114         //簡單計算
115         column.Expression = "value*2";
116         test = table.Select("id='id1'")[0]["exp1"];
117         Console.WriteLine(test);
118         //test=2;
119 
120         //字符串函數
121         column.Expression = "len(id)";
122         test = table.Select("id='id1'")[0]["exp1"];
123         Console.WriteLine(test);
124         //test=3;
125 
126         //字符串函數
127         column.Expression = "len(' '+id+' ')";
128         test = table.Select("id='id1'")[0]["exp1"];
129         Console.WriteLine(test);
130         //test=5;
131 
132         //字符串函數
133         column.Expression = "len(trim(' '+id+' '))";
134         test = table.Select("id='id1'")[0]["exp1"];
135         Console.WriteLine(test);
136         //test=3;
137 
138         //字符串函數
139         column.Expression = "substring(id,3,len(id)-2)";
140         test = table.Select("id='id1'")[0]["exp1"];
141         Console.WriteLine(test);
142         //test=1; //substring的起始字符位置爲1不是0
143 
144         //類型轉換
145         column.Expression = "convert(substring(id,3,len(id)-2),'System.Int32')*1.6";
146         test = table.Select("id='id1'")[0]["exp1"];
147         Console.WriteLine(test);
148         //test=1.6;
149 
150         //至關於sqlserver的isnull
151         column.Expression = "isnull(value,10)";
152         test = table.Select("id='id1'")[0]["exp1"];
153         Console.WriteLine(test);
154         //test=1;
155 
156         //三元運算符,至關於sqlserver的case when
157         column.Expression = "iif(value>5,1000,2000)";
158         test = table.Select("id='id1'")[0]["exp1"];
159         Console.WriteLine(test);
160         //test=2000;
161 
162         //like運算符
163         column.Expression = "iif(id like '%1',1000,2000)";
164         test = table.Select("id='id1'")[0]["exp1"];
165         Console.WriteLine(test);
166         //test=1000;
167 
168         //in運算符
169         column.Expression = "iif(id not in('id1'),1000,2000)";
170         test = table.Select("id='id1'")[0]["exp1"];
171         Console.WriteLine(test);
172         //test=2000;
173 
174         //嵌套的三元運算
175         column.Expression = "iif(value>5,1000,iif(id like '%1',4000,2000))";
176         test = table.Select("id='id1'")[0]["exp1"];
177         Console.WriteLine(test);
178         //test=4000;
179 
180 
181         //客戶端計算所佔總數的百分比
182         column.Expression = "value/sum(value)";
183         test = table.Select("id='id1'")[0]["exp1"];
184         Console.WriteLine(test);
185         //test=0.01818182
186 
187 
188         //客戶端計算差值,好比nba常規賽的勝場差
189         column.Expression = "max(value)-value";
190         test = table.Select("id='id1'")[0]["exp1"];
191         Console.WriteLine(test);
192         //test=9
193 
194 
195         //***********************父子表計算*************************************/
196 
197 
198         //初始化子表,父子表關係
199         DataTable tableChild = new DataTable();
200 
201         tableChild.Columns.Add("id", typeof(string));
202         tableChild.Columns.Add("value", typeof(int));
203 
204         System.Data.DataSet ds = new DataSet();
205         ds.Tables.Add(tableChild);
206         ds.Tables.Add(table);
207         DataRelation relation = new DataRelation("relation", table.Columns["id"], tableChild.Columns["id"]);
208         ds.Relations.Add(relation);
209 
210         for (int i = 1; i <= 10; i++)
211         {
212             System.Data.DataRow dRow = tableChild.NewRow();
213             dRow["id"] = "id1";
214             dRow["value"] = i;
215             tableChild.Rows.Add(dRow);
216         }
217 
218 
219         //計算子表記錄數
220         column.Expression = "count(child(relation).value)";
221         test = table.Select("id='id1'")[0]["exp1"];
222         Console.WriteLine(test);
223         //test=10;
224 
225 
226 
227         //計算父子表的百分比
228         column.Expression = "value/sum(child(relation).value)";
229         test = table.Select("id='id1'")[0]["exp1"];
230         Console.WriteLine(test);
231         //test=0.01818182;
232 
233 
234         //計算父子表的差值,好比父表爲庫存數量，子表爲訂購數量，計算得出須要補充的數量
235         column.Expression = "iif(value-sum(child(relation).value)>0,0,value-sum(child(relation).value))";
236         test = table.Select("id='id1'")[0]["exp1"];
237         Console.WriteLine(test);
238         //test=-54;
239 
240         //比較遺憾的是沒有發現可以計算同比和環比的方法，並且計算列沒法做爲約束
241         //結束，DataTable能夠讓你儘可能發揮聰明才智來減小繁雜的sql語句而且減輕服務器計算符合