C# · 12月 28, 2021

如何在c#中加入两个DataTable?

如何保留外部连接(我认为是外部加入,但我不是100%确定)两个数据表与以下表格和条件,同时保留两个表中的所有列?

dtblLeft:

id col1 anotherColumn2 1 1 any2 2 1 any2 3 2 any2 4 3 any2 5 3 any2 6 3 any2 7 any2

dtblRight:

col1 col2 anotherColumn1 1 Hi any1 2 Bye any1 3 Later any1 4 Never any1

dtblJoined:

id col1 col2 anotherColumn1 anotherColumn2 1 1 Hi any1 any2 2 1 Hi any1 any2 3 2 Bye any1 any2 4 3 Later any1 any2 5 3 Later any1 any2 6 3 Later any1 any2 7 any2

条件:

>在dtblLeft中,col1不需要具有唯一的值.
>在dtblRight中,col1具有唯一的值.
>如果dtblLeft在col1中缺少一个外键,或者它在dtblRight中不存在一个外键,那么将插入空或空字段.
>加入col1.

我可以使用常规的DataTable操作,LINQ或其他.

我尝试了这个,但它删除重复:

dtblA.PrimaryKey = new DataColumn[] {dtblA.Columns[“col1”]}DataTable dtblJoined = new DataTable();dtblJoined.Merge(dtblA,false,MissingSchemaAction.AddWithKey);dtblJoined.Merge(dtblB,MissingSchemaAction.AddWithKey);

编辑1:

这是接近我所想要的,但它只有一个表的列(发现在这link):

dtblJoined = (from t1 in dtblA.Rows.Cast<DaTarow>() join t2 in dtblB.Rows.Cast<DaTarow>() on t1[“col1”] equals t2[“col1”] select t1).CopyToDataTable();

编辑2:

这个link的答案似乎适用于我,但我不得不改变一下如下:

DataTable targetTable = dtblA.Clone();var dt2Columns = dtblB.Columns.OfType<DataColumn>().Select(dc =>new DataColumn(dc.ColumnName,dc.DataType,dc.Expression,dc.ColumnMapping));var dt2FinalColumns = from dc in dt2Columns.AsEnumerable() where targetTable.Columns.Contains(dc.ColumnName) == false select dc;targetTable.Columns.AddRange(dt2FinalColumns.ToArray());var rowData = from row1 in dtblA.AsEnumerable() join row2 in dtblB.AsEnumerable() on row1[“col1”] equals row2[“col1”] select row1.ItemArray.Concat(row2.ItemArray.Where(r2 => row1.ItemArray.Contains(r2) == false)).ToArray(); foreach (object[] values in rowData) targetTable.Rows.Add(values);

我也发现这个link,我可能会尝试,因为它似乎更简洁.

编辑3(11/18/2013):

更新表以反映更多的情况.

解决方法 感谢所有的帮助.这是我根据多种资源提出的: public static class DataTableHelper{ public enum JoinType { /// <summary> /// Same as regular join. Inner join produces only the set of records that match in both Table A and Table B. /// </summary> Inner = 0,/// <summary> /// Same as Left Outer join. Left outer join produces a complete set of records from Table A,with the matching records (where available) in Table B. If there is no match,the right side will contain null. /// </summary> Left = 1 } /// <summary> /// Joins the passed in DataTables on the colToJoinOn. /// <para>Returns an appropriate DataTable with zero rows if the colToJoinOn does not exist in both tables.</para> /// </summary> /// <param name=”dtblLeft”></param> /// <param name=”dtblRight”></param> /// <param name=”colToJoinOn”></param> /// <param name=”joinType”></param> /// <returns></returns> /// <remarks> /// <para>https://stackoverflow.com/questions/2379747/create-combined-datatable-from-two-datatables-joined-with-linq-c-sharp?rq=1</para> /// <para>http://msdn.microsoft.com/en-us/library/vstudio/bb397895.aspx</para> /// <para>http://www.codinghorror.com/blog/2007/10/a-visual-explanation-of-sql-joins.html</para> /// <para>https://stackoverflow.com/questions/406294/left-join-and-left-outer-join-in-sql-server</para> /// </remarks> public static DataTable JoinTwoDataTablesOnOneColumn(DataTable dtblLeft,DataTable dtblRight,string colToJoinOn,JoinType joinType) { //Change column name to a temp name so the LINQ for getting row data will work properly. string strTempColName = colToJoinOn + “_2”; if (dtblRight.Columns.Contains(colToJoinOn)) dtblRight.Columns[colToJoinOn].ColumnName = strTempColName; //Get columns from dtblLeft DataTable dtblResult = dtblLeft.Clone(); //Get columns from dtblRight var dt2Columns = dtblRight.Columns.OfType<DataColumn>().Select(dc => new DataColumn(dc.ColumnName,dc.ColumnMapping)); //Get columns from dtblRight that are not in dtblLeft var dt2FinalColumns = from dc in dt2Columns.AsEnumerable() where !dtblResult.Columns.Contains(dc.ColumnName) select dc; //Add the rest of the columns to dtblResult dtblResult.Columns.AddRange(dt2FinalColumns.ToArray()); //No reason to continue if the colToJoinOn does not exist in both DataTables. if (!dtblLeft.Columns.Contains(colToJoinOn) || (!dtblRight.Columns.Contains(colToJoinOn) && !dtblRight.Columns.Contains(strTempColName))) { if (!dtblResult.Columns.Contains(colToJoinOn)) dtblResult.Columns.Add(colToJoinOn); return dtblResult; } switch (joinType) { default: case JoinType.Inner: #region Inner //get row data //To use the DataTable.AsEnumerable() extension method you need to add a reference to the System.Data.DataSetExtension assembly in your project. var rowDataLeftInner = from rowLeft in dtblLeft.AsEnumerable() join rowRight in dtblRight.AsEnumerable() on rowLeft[colToJoinOn] equals rowRight[strTempColName] select rowLeft.ItemArray.Concat(rowRight.ItemArray).ToArray(); //Add row data to dtblResult foreach (object[] values in rowDataLeftInner) dtblResult.Rows.Add(values); #endregion break; case JoinType.Left: #region Left var rowDataLeftOuter = from rowLeft in dtblLeft.AsEnumerable() join rowRight in dtblRight.AsEnumerable() on rowLeft[colToJoinOn] equals rowRight[strTempColName] into gj from subRight in gj.DefaultIfEmpty() select rowLeft.ItemArray.Concat((subRight== null) ? (dtblRight.NewRow().ItemArray) :subRight.ItemArray).ToArray(); //Add row data to dtblResult foreach (object[] values in rowDataLeftOuter) dtblResult.Rows.Add(values); #endregion break; } //Change column name back to original dtblRight.Columns[strTempColName].ColumnName = colToJoinOn; //Remove extra column from result dtblResult.Columns.Remove(strTempColName); return dtblResult; }}

编辑3:

该方法现在可以正常工作,并且当表具有2000行时,该方法仍然很快.任何建议/建议/改进将不胜感激.

编辑4:

我有一些情况导致我意识到,以前的版本是真正做一个内在的联合.该功能已被修改以解决该问题.我使用这个link的信息来弄清楚.