vb.net 循环遍历数据表 vb
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looping through a data table vb
提问by iDev
I'm trying to loop through a data table that has multiple values for my constraint. How can I keep the first value and add together all the other values that match my constraint.
我正在尝试遍历具有多个约束值的数据表。如何保留第一个值并将与我的约束匹配的所有其他值加在一起。
For i = 0 To ds.Tables(0).Rows.Count - 1
If ds.Tables(0).Rows(i).Item("TEND_POS_ID") = 8 Then
'This only returns the last value
'Value 1 = 2
'Value 2 = 7.5
'should = 9.5 but it is showing 7.5
tmpCoupon = ds.Tables(0).Rows(i).Item("TENDER_AMT")
End If
Next
txtCoupon.Text = tmpCoupon
采纳答案by Steve
If I understand your question correctly, you need to add the values of TENDER_AMTwhere the value in TEND_POS_IDis 8. If this is the case you could use the Selectmethod of the DataTable
如果我正确理解您的问题，您需要添加TENDER_AMT其中值为TEND_POS_ID8的值。如果是这种情况，您可以使用DataTable的Select方法
Dim rows = ds.Tables(0).Select("TEND_POS_ID = 8")
for each r in rows
tmpCoupon += Convert.ToDecimal(r("TENDER_AMD"))
Next
However, rembember that this kind of work (SUM a column grouping by another column) is usually better resolved by the query that you submit to the database. Something like this:
但是，请记住，您提交到数据库的查询通常可以更好地解决此类工作（按另一列对列进行分组）。像这样的东西：
SELECT TEND_POS_ID, SUM(TENDER_AMD) FROM Table1 GROUP BY TEND_POS_ID
