两个DataTable关联查询（inner join、left join）C#代码

  1 using System;
  2 using System.Collections.Generic;
  3 using System.Text;
  4 using System.Data;
  5 
  6 namespace ConsoleApplication1
  7 {
  8     /// <summary>
  9     /// 在返回的table处大断点查看结果
 10     /// </summary>
 11     class Program
 12     {
 13         static void Main(string[] args)
 14         {
 15             CreatTable();
 16         }
 17 
 18         /// <summary>
 19         /// 创建两个测试表
 20         /// </summary>
 21         public static void CreatTable()
 22         {
 23             //定义数据结构
 24             DataTable Ks = new DataTable("客商"); //左表or主表
 25             DataColumn dcID = new DataColumn("ID", System.Type.GetType("System.Int32"));
 26             DataColumn dcNa = new DataColumn("客商名称", System.Type.GetType("System.String"));
 27             Ks.Columns.Add(dcID);
 28             Ks.Columns.Add(dcNa);
 29 
 30             DataTable Dj = new DataTable("订单");//右表or子表
 31             DataColumn dcID2 = new DataColumn("ID", System.Type.GetType("System.Int32"));
 32             DataColumn dcNu = new DataColumn("订单数量", System.Type.GetType("System.Int32"));
 33             Dj.Columns.Add(dcID2);
 34             Dj.Columns.Add(dcNu);
 35 
 36             //左表数据
 37             DataRow KsDt = Ks.NewRow();
 38             KsDt["ID"] = 11;
 39             KsDt["客商名称"] = "张三";
 40             Ks.Rows.Add(KsDt);
 41 
 42             KsDt = Ks.NewRow();
 43             KsDt["ID"] = 12;
 44             KsDt["客商名称"] = "李四";
 45             Ks.Rows.Add(KsDt);
 46 
 47             KsDt = Ks.NewRow();
 48             KsDt["ID"] = 13;
 49             KsDt["客商名称"] = "王武";
 50             Ks.Rows.Add(KsDt);
 51 
 52             KsDt = Ks.NewRow();
 53             KsDt["ID"] = 14;
 54             KsDt["客商名称"] = "赵柳";
 55             Ks.Rows.Add(KsDt);
 56 
 57 
 58             //右表数据
 59             KsDt = Dj.NewRow();
 60             KsDt["ID"] = 11;
 61             KsDt["订单数量"] = 10;
 62             Dj.Rows.Add(KsDt);
 63 
 64             //KsDt = Dj.NewRow();
 65             //KsDt["ID"] = 11;
 66             //KsDt["订单数量"] = 12;
 67             //Dj.Rows.Add(KsDt);
 68 
 69             //KsDt = Dj.NewRow();
 70             //KsDt["ID"] = 12;
 71             //KsDt["订单数量"] = 16;
 72             //Dj.Rows.Add(KsDt);
 73 
 74 
 75             //KsDt = Dj.NewRow();
 76             //KsDt["ID"] = 13;
 77             //KsDt["订单数量"] = 30;
 78             //Dj.Rows.Add(KsDt);
 79 
 80             KsDt = Dj.NewRow();
 81             KsDt["ID"] = 14;
 82             KsDt["订单数量"] = 40;
 83             Dj.Rows.Add(KsDt);
 84 
 85             KsDt = Dj.NewRow();
 86             KsDt["ID"] = 15;
 87             KsDt["订单数量"] = 1250;
 88             Dj.Rows.Add(KsDt);
 89 
 90             /*********************调用******************************************/
 91             //
 92             Join(Ks, Dj, new DataColumn[] { Ks.Columns["ID"] }, new DataColumn[] { Dj.Columns["ID"] });
 93             //重载1
 94             Join(Ks, Dj, Ks.Columns["ID"], Dj.Columns["ID"]);
 95             //重载2
 96             Join(Ks, Dj, "ID", "ID");
 97 
 98             /*********************调用结束**************************************/
 99         }
100 
101         /// <summary>
102         /// 建立两内存表的链接
103         /// </summary>
104         /// <param name="dt1">左表（主表）</param>
105         /// <param name="dt2">右表</param>
106         /// <param name="FJC">左表中关联的字段名（字符串）</param>
107         /// <param name="SJC">右表中关联的字段名（字符串）</param>
108         /// <returns></returns>
109         public static DataTable Join(DataTable dt1, DataTable dt2, DataColumn[] FJC, DataColumn[] SJC)
110         {
111             //创建一个新的DataTable
112             DataTable table = new DataTable("Join");
113 
114             // Use a DataSet to leverage DataRelation
115             using (DataSet ds = new DataSet())
116             {
117                 //把DataTable Copy到DataSet中
118                 ds.Tables.AddRange(new DataTable[] { dt1.Copy(), dt2.Copy() });
119 
120                 DataColumn[] First_columns = new DataColumn[FJC.Length];
121                 for (int i = 0; i < First_columns.Length; i++)
122                 {
123                     First_columns[i] = ds.Tables[0].Columns[FJC[i].ColumnName];
124                 }
125 
126                 DataColumn[] Second_columns = new DataColumn[SJC.Length];
127                 for (int i = 0; i < Second_columns.Length; i++)
128                 {
129                     Second_columns[i] = ds.Tables[1].Columns[SJC[i].ColumnName];
130                 }
131 
132                 //创建关联
133                 DataRelation r = new DataRelation(string.Empty, First_columns, Second_columns, false);
134                 ds.Relations.Add(r);
135 
136                 //为关联表创建列
137                 for (int i = 0; i < dt1.Columns.Count; i++)
138                 {
139                     table.Columns.Add(dt1.Columns[i].ColumnName, dt1.Columns[i].DataType);
140                 }
141 
142                 for (int i = 0; i < dt2.Columns.Count; i++)
143                 {
144                     //看看有没有重复的列，如果有在第二个DataTable的Column的列明后加_Second
145                     if (!table.Columns.Contains(dt2.Columns[i].ColumnName))
146                         table.Columns.Add(dt2.Columns[i].ColumnName, dt2.Columns[i].DataType);
147                     else
148                         table.Columns.Add(dt2.Columns[i].ColumnName + "_Second", dt2.Columns[i].DataType);
149                 }
150 
151                 table.BeginLoadData();
152                 int itable2Colomns = ds.Tables[1].Rows[0].ItemArray.Length;
153                 foreach (DataRow firstrow in ds.Tables[0].Rows)
154                 {
155                     //得到行的数据
156                     DataRow[] childrows = firstrow.GetChildRows(r);//第二个表关联的行
157                     if (childrows != null && childrows.Length > 0)
158                     {
159                         object[] parentarray = firstrow.ItemArray;
160                         foreach (DataRow secondrow in childrows)
161                         {
162                             object[] secondarray = secondrow.ItemArray;
163                             object[] joinarray = new object[parentarray.Length + secondarray.Length];
164                             Array.Copy(parentarray, 0, joinarray, 0, parentarray.Length);
165                             Array.Copy(secondarray, 0, joinarray, parentarray.Length, secondarray.Length);
166                             table.LoadDataRow(joinarray, true);
167                         }
168 
169                     }
170                     else//如果有外连接(Left Join)添加这部分代码
171                     {
172                         object[] table1array = firstrow.ItemArray;//Table1
173                         object[] table2array = new object[itable2Colomns];
174                         object[] joinarray = new object[table1array.Length + itable2Colomns];
175                         Array.Copy(table1array, 0, joinarray, 0, table1array.Length);
176                         Array.Copy(table2array, 0, joinarray, table1array.Length, itable2Colomns);
177                         table.LoadDataRow(joinarray, true);
178                         DataColumn[] dc = new DataColumn[2];
179                         dc[0] = new DataColumn("");
180                     }
181                 }
182                 table.EndLoadData();
183             }
184             return table;//***在此处打断点，程序运行后点击查看即可观察到结果
185         }
186 
187         /// <summary>
188         /// 重载1
189         /// </summary>
190         /// <param name="dt1"></param>
191         /// <param name="dt2"></param>
192         /// <param name="FJC"></param>
193         /// <param name="SJC"></param>
194         /// <returns></returns>
195         public static DataTable Join(DataTable dt1, DataTable dt2, DataColumn FJC, DataColumn SJC)
196         {
197             return Join(dt1, dt2, new DataColumn[] { FJC }, new DataColumn[] { SJC });
198         }
199 
200         /// <summary>
201         /// 重载2
202         /// </summary>
203         /// <param name="dt1"></param>
204         /// <param name="dt2"></param>
205         /// <param name="FJC"></param>
206         /// <param name="SJC"></param>
207         /// <returns></returns>
208         public static DataTable Join(DataTable dt1, DataTable dt2, string FJC, string SJC)
209         {
210             return Join(dt1, dt2, new DataColumn[] { dt1.Columns[FJC] }, new DataColumn[] { dt1.Columns[SJC] });
211         }
212 
213     }
214 }