LEFT OUTER JOIN 2数据表 [英] LEFT OUTER JOIN 2 datatables

问题描述

我想了解如何查询，最好用LINQ，2数据表。
我愿做一个LEFT OUTER JOIN他们

I'm trying to understand how to query, preferably with LINQ, 2 datatables. I would like to do a LEFT OUTER JOIN on them

Datatable1与COL的：[ID] [可口可乐]

DataTable2与山坳的：。[ID] [COLB] [COLC] ...

Datatable1 with col's: [ID] [colA]
DataTable2 with col's: [ID] [ColB] [ColC] ...

希望加入上ID

是否有人可以告诉我一个例子，所以我可以将其应用到数据表我有吗？谢谢你在前进

Can someone please show me an example so I can apply it to the datatables I have? Thank you in advance

推荐答案

这编译并执行你根据给定结果集所期望的：

This compiles and does what you would expect based on the result set given:

// create the default row to be used when no value found
var defaultRow = DataTable2.NewRow();
defaultRow[0] = 0;
defaultRow[1] = String.Empty;

// the query
var result = from x in DataTable1.AsEnumerable()
    join y in DataTable2.AsEnumerable() on (string)x["ID"] equals (string)y["ID"] 
             into DataGroup
    from row in DataGroup.DefaultIfEmpty<DataRow>(defaultRow)
    select new {a = x["ColA"], b = (string)row["ColB"]};

这篇关于LEFT OUTER JOIN 2数据表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！