Question

我需要将两个数据模式合并为一个。我有Schema1和Schema2。我需要将这两个加入Schema3。此外，我有一个查询数据集的Select语句，但我无法弄清楚如何在包含两个表（Schema1和Schema2）的数据集上使用select语句，并将它们组合到新表schema3中，即同一数据集中的表由两个表的字段组成。

实施例

架构1 ID，餐饮，书，白饭，洞穴

架构2 ID ，地毯，弦乐，运行

架构3 ID，餐饮，书，白饭，洞穴，地毯，弦乐，运行

使用此命令填充Schema3表

Sql命令：

Select * Schema1 [except ID] and all fields from Schema2 [exceptID] Inner Join 
Schema2 ON Schema1.ID = Schema2.ID
Where ID = {dynamically defined variable 'X'}

请原谅缺乏正确的语法。这里的主要问题是使用select语句查询数据集并使用结果填充表。我没有完全连接到我的数据库，因为我已经在本地填充了一个数据集。

------编辑------ 我真的只需要一种方法来从两个表的查询中创建一个数据行数组。

Answer 1

您可以在此处使用此扩展方法，我最近从头开始编写another question。它允许通过公共密钥合并多个表。如果未指定密钥，则只使用默认的DataTable.Merge方法：

public static DataTable MergeAll(this IList<DataTable> tables, String primaryKeyColumn)
{
    if (!tables.Any())
        throw new ArgumentException("Tables must not be empty", "tables");
    if(primaryKeyColumn != null)
        foreach(DataTable t in tables)
            if(!t.Columns.Contains(primaryKeyColumn))
                throw new ArgumentException("All tables must have the specified primarykey column " + primaryKeyColumn, "primaryKeyColumn");

    if(tables.Count == 1)
        return tables[0];

    DataTable table = new DataTable("TblUnion");
    table.BeginLoadData(); // Turns off notifications, index maintenance, and constraints while loading data
    foreach (DataTable t in tables)
    {
        table.Merge(t); // same as table.Merge(t, false, MissingSchemaAction.Add);
    }
    table.EndLoadData();

    if (primaryKeyColumn != null)
    {
        // since we might have no real primary keys defined, the rows now might have repeating fields
        // so now we're going to "join" these rows ...
        var pkGroups = table.AsEnumerable()
            .GroupBy(r => r[primaryKeyColumn]);
        var dupGroups = pkGroups.Where(g => g.Count() > 1);
        foreach (var grpDup in dupGroups)
        { 
            // use first row and modify it
            DataRow firstRow = grpDup.First();
            foreach (DataColumn c in table.Columns)
            {
                if (firstRow.IsNull(c))
                {
                    DataRow firstNotNullRow = grpDup.Skip(1).FirstOrDefault(r => !r.IsNull(c));
                    if (firstNotNullRow != null)
                        firstRow[c] = firstNotNullRow[c];
                }
            }
            // remove all but first row
            var rowsToRemove = grpDup.Skip(1);
            foreach(DataRow rowToRemove in rowsToRemove)
                table.Rows.Remove(rowToRemove);
        }
    }

    return table;
}

您可以这样称呼它：

var tables= new[] { Schema1, Schema2};
DataTable Schema3 = tables.MergeAll("ID");

修改：如果您不需要使用合并架构的新DataTable，您还可以使用Linq-To-DataSet（现在是VB.NET）：

Dim schema3 = From r1 In schema1
          Join r2 In schema2 On r1.Field(Of Int32)("ID") Equals r2.Field(Of Int32)("ID")
          Select New With {
                .ID = r1.Field(Of Int32)("ID"),
                .Food = r1.Field(Of String)("Food"),
                .Book = r1.Field(Of String)("Book"),
                .Rice = r1.Field(Of String)("Rice"),
                .Cave = r1.Field(Of String)("Cave"),
                .Carpet = r2.Field(Of String)("Carpet"),
                .Strings = r2.Field(Of String)("Strings"),
                .Run = r2.Field(Of String)("Run")
            }

Answer 2

试试这个：

  ''' <summary>
  ''' Merge two datatables that have a 1:1 relationship
  ''' </summary>
  ''' <param name="dtb1">Required Datatable.</param>
  ''' <param name="dtb2">Required Datatable.</param>
  ''' <param name="dtb1MatchField">Required String. Field name in dtb1 to use to match records</param>
  ''' <param name="dtb2MatchField">Required String. Field name in dtb2 to use to match records</param>
  ''' <remarks></remarks>'
  Private Function MergeDataTables(ByVal dtb1 As DataTable, ByVal dtb2 As DataTable, ByVal dtb1MatchField As String, ByVal dtb2MatchField As String) As DataTable
    Dim dtbOutput As DataTable = dtb1.Copy
    Dim lstSkipFields As New List(Of String)
    For Each dcl As DataColumn In dtb2.Columns
      Try
        dtbOutput.Columns.Add(dcl.ColumnName, dcl.DataType)
      Catch ex As DuplicateNameException
        lstSkipFields.Add(dcl.ColumnName)
      End Try
    Next dcl
    'Merge dtb2 records that match existing records in dtb1'
    Dim dtb2Temp As DataTable = dtb2.Copy
    For int2 As Integer = dtb2Temp.Rows.Count - 1 To 0 Step -1
      Dim drw2 As DataRow = dtb2Temp.Rows(int2)
      Dim o2 As Object = drw2(dtb2MatchField)
      For Each drw1 As DataRow In dtbOutput.Rows
        Dim o1 As Object = drw1(dtb1MatchField)
        If o1.ToString = o2.ToString Then
          For Each dcl As DataColumn In dtb2Temp.Columns
            If Not lstSkipFields.Contains(dcl.ColumnName) Then
              drw1(dcl.ColumnName) = drw2(dcl.ColumnName)
            End If
          Next dcl
          dtb2Temp.Rows.Remove(drw2)
        End If
      Next drw1
    Next int2
    'add rows that weren not in dtb1'
    For Each drw2 As DataRow In dtb2Temp.Rows
      Dim drw1 As DataRow = dtbOutput.NewRow
      For Each dcl As DataColumn In dtb2Temp.Columns
        drw1(dcl.ColumnName) = drw2(dcl.ColumnName)
      Next dcl
      dtbOutput.Rows.Add(drw1)
    Next drw2
    Return dtbOutput
  End Function

将两个表合并为一个

2 个答案: