vb.net 中 sql查詢出來(lái)的值，比如books中的remainnum,賦給一個(gè)變量 num，再將num-1之后update到remainnum中

Dim num As Integer

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Dim connstr, insertcmd, selectcmd As String

connstr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=D:\360data\重要數(shù)據(jù)\我的文檔\hd.mdb"

Dim conn As OleDbConnection

Dim cmd, cmd1 As OleDbCommand

conn = New OleDbConnection(connstr)

Dim r As OleDbDataReader

conn.Open()

insertcmd = "insert into returnbooks (aid,aname,ISBN,bname,renum,reday) values("

Val(ComboBox1.Text) ",'"

TextBox2.Text "','"

ComboBox2.Text "','"

TextBox2.Text "',"

Val(TextBox3.Text) ",'"

CType(TextBox4.Text, Date) "' )"

cmd = New OleDbCommand(insertcmd, conn)

cmd.ExecuteNonQuery()

updatecmd = "update books set remainnum=" Val(num) "-" Val(TextBox3.Text) " where ISBN='" ComboBox2.Text "'"

cmd = New OleDbCommand(updatecmd, conn)

cmd.ExecuteNonQuery()

updatecmd = "select remainnum as num from books where ISBN= '" ComboBox2.Text "'"

cmd = New OleDbCommand(updatecmd, conn)

cmd.ExecuteNonQuery()

updatecom = "update books set remainnum=num+ " Val(TextBox3.Text) ""

cmd = New OleDbCommand(updatecmd, conn)

cmd.ExecuteNonQuery()

selectcmd = "select remainnum from books where ISBN='" ComboBox2.Text "'"

cmd1 = New OleDbCommand(selectcmd, conn)

r = cmd1.ExecuteReader()

If (r.Read()) Then '如果sql查詢到了數(shù)據(jù)

num = r.GetInt32(0)

End If

conn.Close()

/*注意代碼的格式，不然改起來(lái)太費(fèi)時(shí)間*/

求《VB.net入門經(jīng)典（第四版）》電子書

電子書太大，發(fā)布過(guò)去，樓主可以到網(wǎng)站上下載

;restype=-1id=10000001ty=0

求VB.NET 參考文獻(xiàn)

中文的話，這里有個(gè)網(wǎng)站你可以去看看，上面搜羅了很多相關(guān)的書，

如果是英語(yǔ)的話，《Beginning VB.NET 2003》，作者：Thearon Willis, Jonathan Crossland, Richard Blair,其他信息：Wrox（出版社）; 3 Sub edition | ISBN:0764556584 | 840 pages | April 9, 2004 | CHM | 32 Mb

vb.net操作xml數(shù)據(jù)庫(kù)(急)

使用System.XML

Imports Microsoft.VisualBasic

Imports System

Imports System.IO

Imports System.Xml

namespace HowTo.Samples.XML

public class WriteXmlFileSample

private const document as string = "newbooks.xml"

shared sub Main()

Dim myWriteXmlFileSample as WriteXmlFileSample

myWriteXmlFileSample = new WriteXmlFileSample()

myWriteXmlFileSample.Run(document)

end sub

public sub Run(args As String)

Dim myXmlTextReader as XmlTextReader = nothing

Dim myXmlTextWriter as XmlTextWriter = nothing

try

myXmlTextWriter = new XmlTextWriter (args, nothing)

myXmlTextWriter.Formatting = System.Xml.Formatting.Indented

myXmlTextWriter.WriteStartDocument(false)

myXmlTextWriter.WriteDocType("bookstore", nothing, "books.dtd", nothing)

myXmlTextWriter.WriteComment("此文件表示書店庫(kù)存數(shù)據(jù)庫(kù)的另一個(gè)片斷")

myXmlTextWriter.WriteStartElement("bookstore")

myXmlTextWriter.WriteStartElement("book", nothing)

myXmlTextWriter.WriteAttributeString("genre","autobiography")

myXmlTextWriter.WriteAttributeString("publicationdate","1979")

myXmlTextWriter.WriteAttributeString("ISBN","0-7356-0562-9")

myXmlTextWriter.WriteElementString("title", nothing, "The Autobiography of Mark Twain")

myXmlTextWriter.WriteStartElement("Author", nothing)

myXmlTextWriter.WriteElementString("first-name", "Mark")

myXmlTextWriter.WriteElementString("last-name", "Twain")

myXmlTextWriter.WriteEndElement()

myXmlTextWriter.WriteElementString("price", "7.99")

myXmlTextWriter.WriteEndElement()

myXmlTextWriter.WriteEndElement()

'向文件寫 XML 并關(guān)閉編寫器

myXmlTextWriter.Flush()

myXmlTextWriter.Close()

' 讀取返回的文件并進(jìn)行分析以確保正確生成 XML

myXmlTextReader = new XmlTextReader (args)

FormatXml (myXmlTextReader, args)

catch e as Exception

Console.WriteLine ("異常：{0}", e.ToString())

finally

Console.WriteLine()

Console.WriteLine("對(duì)文件 {0} 的處理已完成。", args)

If Not myXmlTextReader Is Nothing

myXmlTextReader.Close()

end if

'關(guān)閉編寫器

If Not myXmlTextWriter Is Nothing

myXmlTextWriter.Close()

end if

End try

End Sub

private shared Sub FormatXml (reader as XmlTextReader, filename as String)

Dim piCount, docCount, commentCount, elementCount as Integer

Dim attributeCount, textCount, whitespaceCount as Integer

While reader.Read()

Select (reader.NodeType)

case XmlNodeType.ProcessingInstruction:

Format (reader, "ProcessingInstruction")

piCount += 1

case XmlNodeType.DocumentType:

Format (reader, "DocumentType")

docCount += 1

case XmlNodeType.Comment:

Format (reader, "Comment")

commentCount += 1

case XmlNodeType.Element:

Format (reader, "Element")

elementCount += 1

While reader.MoveToNextAttribute()

Format (reader, "Attribute")

end While

if (reader.HasAttributes)

attributeCount += reader.AttributeCount

end if

case XmlNodeType.Text:

Format (reader, "Text")

textCount += 1

case XmlNodeType.Whitespace:

whitespaceCount += 1

End Select

End While

' 顯示該文件的統(tǒng)計(jì)信息

Console.WriteLine ()

Console.WriteLine("{0} 文件的統(tǒng)計(jì)信息", filename)

Console.WriteLine ()

Console.WriteLine("處理指令：" piCount)

Console.WriteLine("文檔類型：" docCount)

Console.WriteLine("注釋：" commentCount)

Console.WriteLine("元素：" elementCount)

Console.WriteLine("屬性：" attributeCount)

Console.WriteLine("文本：" textCount)

Console.WriteLine("空白：" whitespaceCount)

End Sub

private shared Sub Format(byref reader as XmlTextReader , NodeType as String)

' 格式化輸出

Console.Write(reader.Depth " ")

Console.Write(reader.AttributeCount " ")

Dim i as Integer

for i = 0 to reader.Depth - 1

Console.Write(Strings.chr(9))

Next

Console.Write(reader.Prefix NodeType "" reader.Name "" reader.Value)

Console.WriteLine()

End Sub

End Class

End Namespace

參考: