SQL查询未在VB.NET中运行
我对VB.NET比较熟悉,我试图在VB.NET中执行SQL查询,但在输出时不显示任何值。你能帮我找出哪里出了问题吗SQL查询未在VB.NET中运行,sql,sql-server,vb.net,Sql,Sql Server,Vb.net,我对VB.NET比较熟悉,我试图在VB.NET中执行SQL查询,但在输出时不显示任何值。你能帮我找出哪里出了问题吗 Dim sConnectionString As String _ = "User ID=XXX ;Password=XXX;Initial Catalog=gemXXX;Data Source=SCRBAMSDKBXXXXXX" Dim objConn As New SqlConnection(sConnectionString) objConn.Ope
Dim sConnectionString As String _
= "User ID=XXX ;Password=XXX;Initial Catalog=gemXXX;Data Source=SCRBAMSDKBXXXXXX"
Dim objConn As New SqlConnection(sConnectionString)
objConn.Open()
Dim sw ,readerObj
Dim sSQL As String = "select top 1 " & sw & " = e.import from tblrelcoms r , [beant].[dbo].tblequipments e where r.IDEquipment = e.IDEquipment"
Using readerObj As SqlClient.SqlDataReader = cmdObj.ExecuteReader
Dim objCmd As New SqlCommand(sSQL, objConn)
objCmd.ExecuteNonQuery()
TextBox1.Text = sw.ToString()
您所面临的问题是,您不能仅仅将一个变量连接到SQL中,并期望它在SQL执行后得到更新 ExecuteScalar可能是实现您想要的最简单的方法:
Dim sConnectionString As String _
= "User ID=XXX ;Password=XXX;Initial Catalog=gemXXX;Data Source=SCRBAMSDKBXXXXXX"
Dim sSQL as string = "SELECT TOP 1 e.import " _
"FROM tblrelcoms r " & _
" INNER JOIN [beant].[dbo].tblequipments e " & _
" ON r.IDEquipment = e.IDEquipment " & _
"ORDER BY e.Import;"
Using connection = new SqlConnection(sConnectionString)
Using command = New SqlCommand(sSQL, connection)
connection.Open()
TextBox1.Text = command.ExecuteScalar().ToString()
End Using
End Using
如果您需要多个列,则可以使用数据读取器:
Dim sConnectionString As String _
= "User ID=XXX ;Password=XXX;Initial Catalog=gemXXX;Data Source=SCRBAMSDKBXXXXXX"
Dim sSQL as string = "SELECT TOP 1 e.import " _
"FROM tblrelcoms r " & _
" INNER JOIN [beant].[dbo].tblequipments e " & _
" ON r.IDEquipment = e.IDEquipment " & _
"ORDER BY e.Import;"
Using connection = new SqlConnection(sConnectionString)
Using command = New SqlCommand(sSQL, connection)
connection.Open()
Using reader = command.ExecuteReader()
If reader.Read()
TextBox1.Text = reader.GetString(0)
End If
End Using
End Using
End Using
我也做了一些其他的改变
,以确保正确处置IDisposable
对象
orderby
子句TOP 1
如果没有order by,将给出不确定的结果(除非您只有一条记录,在这种情况下TOP 1是多余的)*请原谅任何语法错误,我已经多年没有使用VB.Net了,下面可能会有一些c#怪癖,比如我记不起你是否不必为无参数方法使用括号,或者如果你不能。。。希望有足够的基本结构让您开始您遇到的问题是,您不能将变量连接到SQL中,并期望它在SQL执行后得到更新 ExecuteScalar可能是实现您想要的最简单的方法:
Dim sConnectionString As String _
= "User ID=XXX ;Password=XXX;Initial Catalog=gemXXX;Data Source=SCRBAMSDKBXXXXXX"
Dim sSQL as string = "SELECT TOP 1 e.import " _
"FROM tblrelcoms r " & _
" INNER JOIN [beant].[dbo].tblequipments e " & _
" ON r.IDEquipment = e.IDEquipment " & _
"ORDER BY e.Import;"
Using connection = new SqlConnection(sConnectionString)
Using command = New SqlCommand(sSQL, connection)
connection.Open()
TextBox1.Text = command.ExecuteScalar().ToString()
End Using
End Using
如果您需要多个列,则可以使用数据读取器:
Dim sConnectionString As String _
= "User ID=XXX ;Password=XXX;Initial Catalog=gemXXX;Data Source=SCRBAMSDKBXXXXXX"
Dim sSQL as string = "SELECT TOP 1 e.import " _
"FROM tblrelcoms r " & _
" INNER JOIN [beant].[dbo].tblequipments e " & _
" ON r.IDEquipment = e.IDEquipment " & _
"ORDER BY e.Import;"
Using connection = new SqlConnection(sConnectionString)
Using command = New SqlCommand(sSQL, connection)
connection.Open()
Using reader = command.ExecuteReader()
If reader.Read()
TextBox1.Text = reader.GetString(0)
End If
End Using
End Using
End Using
我也做了一些其他的改变
,以确保正确处置IDisposable
对象
orderby
子句TOP 1
如果没有order by,将给出不确定的结果(除非您只有一条记录,在这种情况下TOP 1是多余的)*请原谅任何语法错误,我已经多年没有使用VB.Net了,下面可能会有一些c#怪癖,比如我记不起你是否不必为无参数方法使用括号,或者如果你不能。。。希望有足够的基本结构让您开始您的var
sw
,您不会给它任何值…打开用于执行不返回任何数据的查询的选项StrightExecuteNonQuery。它用于执行sql语句,如update、insert、delete等。ok…但是如何在VB.NET变量中存储sql查询变量的值如果readerObj.HasRows,那么readerObj.read()TextBox1.Text=rdr(“yourcolumnname”)诸如此类?您的varsw
,您不给它任何值…启用用于执行不返回任何数据的查询的选项StrightExecuteNonQuery。它用于执行sql语句,如update、insert、delete等。ok…但是如何在VB.NET变量中存储sql查询变量的值如果readerObj.HasRows,那么readerObj.read()TextBox1.Text=rdr(“yourcolumnname”)之类的语句?很好的例子,这一个将适用于OP!感谢您实际使用和语句,有太多次我看不到这一点…很好的例子,这一个将适用于OP!感谢您实际使用和语句,有太多次我看不到这一点。。。