从另一个数据表中存在的数据表中删除行 [英] Delete rows from a data table that exists in another data table

问题描述

大家好，



如何在不使用for循环的情况下从另一个数据表中存在的数据表中删除行？因此，如果逐一比较，它会减慢过程。



Bcz两个数据表都有超过2万行，而用于循环，会减慢进程，所以任何其他方式删除？



如何一次删除？



什么我试过了：

Hi All,

how to delete rows from a data table that exists in another data table without using for loop ? so if compare one by one , it slow the process.

Bcz both data table got more then 2 lakhs rows,while use for loop, it will slow the process, so any other way to remove ?

How to delete with one shot ?

What I have tried:

Dim dt1 As New DataTable()
dt1.Columns.Add("Name")
dt1.Rows.Add("Apple")
dt1.Rows.Add("Banana")
dt1.Rows.Add("Orange")
 
Dim dt2 As New DataTable()
dt2.Columns.Add("Name")
dt2.Rows.Add("Apple")
dt2.Rows.Add("Banana")
 
Dim rows_to_remove As New List(Of DataRow)()
For Each row1 As DataRow In dt1.Rows
    For Each row2 As DataRow In dt2.Rows
        If row1("Name").ToString() = row2("Name").ToString() Then
            rows_to_remove.Add(row1)
        End If
    Next
Next
 
For Each row As DataRow In rows_to_remove
    dt1.Rows.Remove(row)
    dt1.AcceptChanges()
Next


For example i gave 3 and 2 datas, but actually it retrieve  from database more than 2 lakhs data.

Regards,
Aravind

推荐答案

不，没有使用<删除数据的机会 For ... Next loop。

注意：你正在使用 For ... Next 循环3次。您只能将其缩短为一个循环。怎么样？通过 Name 字段连接表以获取两个表的常见记录，然后从 dt1 中删除​​它。

No, there's no chance to remove data without using For...Next loop.
Note: you're using For...Next loop 3 times. You can short it to one loop only. How? Join tables by Name field to get common records for both tables, then remove it from dt1.

Dim rows_to_remove = From a In dt1.AsEnumerable() Join b In dt2.AsEnumerable() On a.Field(Of String)("Name") Equals b.Field(Of String)("Name")
	Select a
'returns:
'Apple 
'Banana 

你可以使用Linq 除了 [ ^ ]方法：

You can use Linq Except[^] method too:

Dim rows_to_remove = dt2.AsEnumerable.Except(dt1.AsEnumerable())
'returns:
'Apple 
'Banana 

但是！我会通过使用Transact SQL在服务器端执行此操作。请参阅： DELETE（Transact-SQL）| Microsoft Docs [ ^ ]

But! I'd do that on server side by using Transact SQL. See: DELETE (Transact-SQL) | Microsoft Docs[^]

DELETE 
FROM Table1 
WHERE FieldName1 IN (SELECT FieldName1 FROM Table2)

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