1 DataTable dt = new DataTable();
2 //嵌套的三元运算 牛叉到五体投地
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 //计算常量，可以没有初始化列
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;常数计算和filter无关
21
22 test = table.Compute("abs(1)", "");
23 Console.WriteLine(test);
24 //test=null，不知道为这个什么没有报错，而且返回null,其他的数学函数都会抱错
25
26 test = table.Compute("2%2", "");
27 Console.WriteLine(test);
28 //test=0;
29 //其他函数参考下面的计算列
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 ////抛出异常，这里必须是聚合函数
49
50
51
52 //*************************************支持的聚合函数**********************//
53
54 //求数量
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 ////抛出异常，这里不能是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 //统计标准偏差
92 test = table.Compute("StDev(value)", "");
93 Console.WriteLine(test);
94 //test=3.02765035409749
95
96 //统计方差
97 test = table.Compute("Var(value)", "");
98 Console.WriteLine(test);
99 //test=9.16666666666667
100
101
102 //复杂计算
103 test = table.Compute("max(value)/sum(value)", "");
104 Console.WriteLine(test);
105 //test=0.181818181818182
106
107 /**/
108 /*******************************************计算列*************************/
109
110 System.Data.DataColumn column = new DataColumn("exp1", typeof(float));
111 table.Columns.Add(column);
112
113
114 //简单计算
115 column.Expression = "value*2";
116 test = table.Select("id='id1'")[0]["exp1"];
117 Console.WriteLine(test);
118 //test=2;
119
120 //字符串函数
121 column.Expression = "len(id)";
122 test = table.Select("id='id1'")[0]["exp1"];
123 Console.WriteLine(test);
124 //test=3;
125
126 //字符串函数
127 column.Expression = "len(' '+id+' ')";
128 test = table.Select("id='id1'")[0]["exp1"];
129 Console.WriteLine(test);
130 //test=5;
131
132 //字符串函数
133 column.Expression = "len(trim(' '+id+' '))";
134 test = table.Select("id='id1'")[0]["exp1"];
135 Console.WriteLine(test);
136 //test=3;
137
138 //字符串函数
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的起始字符位置为1不是0
143
144 //类型转换
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 //相当于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 //三元运算符,相当于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运算符
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运算符
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 //嵌套的三元运算
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 //客户端计算所占总数的百分比
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 //客户端计算差值,比如nba常规赛的胜场差
189 column.Expression = "max(value)-value";
190 test = table.Select("id='id1'")[0]["exp1"];
191 Console.WriteLine(test);
192 //test=9
193
194
195 //***********************父子表计算*************************************/
196
197
198 //初始化子表,父子表关系
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 //计算子表记录数
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 //计算父子表的百分比
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 //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
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
241 //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
