将n个DataTable组合到单个DataTable中

Question

总之,有一些问题,但我似乎无法提取足够的信息来解决我的问题.我将未知数量的表提取到SQL Server"Tab1","Tab2","Tab3",......,"TabN"中.这些表中的列不同,但行定义相同.我需要将服务器中的所有数据拉入N DataTables,然后将它们组合成一个数据DataTable.我现在所做的是

int nTmpVolTabIdx = 1;
strSqlTmp = String.Empty;
using (DataTable dataTableALL = new DataTable())
{
    while (true)
    {
        string strTmpVolName = String.Format("Tab{0}", nTmpVolTabIdx);
        strSqlTmp = String.Format("SELECT * FROM [{0}];", strTmpVolName);

        // Pull the data from 'VolX' into a local DataTable.
        using (DataTable dataTable = UtilsDB.DTFromDB(conn, strTmpVolName, strSqlTmp, false))
        {
            if (dataTable == null)
                break;
            else
                dataTableALL.Merge(dataTable);
        }
        nTmpVolTabIdx++;
    }
    ...
}

这将合并DataTables但它们未对齐(将空白单元格填充到附加数据集上).我可以DataTable通过循环追加新的列; 但有没有更简单/更好的方法(也许使用LINQ)？

谢谢你的时间.

编辑.提供示例数据集.

我需要的是

个别表是

在第一次合并操作后,我有以下内容

再次感谢.

Answer 1

该表后面有重复的主键,Merge因为没有定义主键.所以要么指定PK,要么尝试这个我从头开始写的方法(所以它没有真正测试过):

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;
}

你可以用这种方式调用它:

var tables = new[] { tblA, tblB, tblC };
DataTable TblUnion = tables.MergeAll("c1");

使用此示例数据:

var tblA = new DataTable();
tblA.Columns.Add("c1", typeof(int));
tblA.Columns.Add("c2", typeof(int));
tblA.Columns.Add("c3", typeof(string));
tblA.Columns.Add("c4", typeof(char));

var tblB = new DataTable();
tblB.Columns.Add("c1", typeof(int));
tblB.Columns.Add("c5", typeof(int));
tblB.Columns.Add("c6", typeof(string));
tblB.Columns.Add("c7", typeof(char));

var tblC = new DataTable();
tblC.Columns.Add("c1", typeof(int));
tblC.Columns.Add("c8", typeof(int));
tblC.Columns.Add("c9", typeof(string));
tblC.Columns.Add("c10", typeof(char));

tblA.Rows.Add(1, 8500, "abc", 'A');
tblA.Rows.Add(2, 950, "cde", 'B');
tblA.Rows.Add(3, 150, "efg", 'C');
tblA.Rows.Add(4, 850, "ghi", 'D');
tblA.Rows.Add(5, 50, "ijk", 'E');

tblB.Rows.Add(1, 7500, "klm", 'F');
tblB.Rows.Add(2, 900, "mno", 'G');
tblB.Rows.Add(3, 150, "opq", 'H');
tblB.Rows.Add(4, 850, "qrs", 'I');
tblB.Rows.Add(5, 50, "stu", 'J');

tblC.Rows.Add(1, 7500, "uvw", 'K');
tblC.Rows.Add(2, 900, "wxy", 'L');
tblC.Rows.Add(3, 150, "yza", 'M');
tblC.Rows.Add(4, 850, "ABC", 'N');
tblC.Rows.Add(5, 50, "CDE", 'O');

之后DataTable.Merge在MergeAll:

经过一些修改后加入行MergeAll:

更新

由于这个问题出现在其中一个注释中,如果两个表之间的唯一关系是表中a的索引,DataRow并且您希望根据索引合并两个表:

public static DataTable MergeTablesByIndex(DataTable t1, DataTable t2)
{
    if (t1 == null || t2 == null) throw new ArgumentNullException("t1 or t2", "Both tables must not be null");

    DataTable t3 = t1.Clone();  // first add columns from table1
    foreach (DataColumn col in t2.Columns)
    {
        string newColumnName = col.ColumnName;
        int colNum = 1;
        while (t3.Columns.Contains(newColumnName))
        {
            newColumnName = string.Format("{0}_{1}", col.ColumnName, ++colNum);
        }
        t3.Columns.Add(newColumnName, col.DataType);
    }
    var mergedRows = t1.AsEnumerable().Zip(t2.AsEnumerable(),
        (r1, r2) => r1.ItemArray.Concat(r2.ItemArray).ToArray());
    foreach (object[] rowFields in mergedRows)
        t3.Rows.Add(rowFields);

    return t3;
}

样品:

var dt1 = new DataTable();
dt1.Columns.Add("ID", typeof(int));
dt1.Columns.Add("Name", typeof(string));
dt1.Rows.Add(1, "Jon");
var dt2 = new DataTable();
dt2.Columns.Add("Country", typeof(string));
dt2.Rows.Add("US");

var dtMerged = MergeTablesByIndex(dt1, dt2);

结果表包含三列ID,Name,Country和单行:1 Jon US