Vb.net和Sqlserver [英] Vb.net and Sqlserver

问题描述

如何检查记录是否存在?而且当记录不存在时我也可以插入记录

How can check the record is exists or not? And also i can insert the record when its not existing

Private Sub AddButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles AddButton.Click
            con = New SqlConnection(Constr)
            con.Open()
            Dim cmdstr1 As String = "Select * from Mcdaily where Mcno=''" & McnoCombo.Text & "''and Ftime=" & DGVlogentry.Item(2, i).Value & ""
            dt = DataManager.ExecuteQuery(cmdstr1, Constr)
            If (dt.Rows.Count > 0) Then
                MessageBox.Show("Already Exists")
            Else
                 Insertcmd()
             End if 
End sub

推荐答案

用于检查的代码已经存在.
那么您的问题在哪里?

You code for checking is already there.
So where is your problem?

此代码正确，您在哪里打了?

我的一点建议.
您可以使用选择计数(*)......."而不是选择* .......".
然后，您可以使用ExecuteScalar()方法，该方法将直接返回行数，并且不需要使用数据表.
只是一个建议. :)

顺便说一句，您面临什么问题?

This code is correct, where are you struck?

A little suggestion from me.
You can use "select count(*)......." rather than "select *.......".
Then you can use ExecuteScalar() method which will directly return count of rows and you won''t need a datatable to work with.
Just a suggestion. :)

BTW, what problem you are facing?

还使用参数而不是将字符串连接到SQL文本.有关更多信息: SqlParameter [

Also use parameters instead of concatenating string to the SQL text. For more info: SqlParameter[^]

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