unit4.~pas

图书管理系统设计程序

unit Unit4;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, DB, ADODB;

type
  Tbook_delete = class(TForm)
    Label1: TLabel;
    GroupBox1: TGroupBox;
    Label2: TLabel;
    Label3: TLabel;
    book_no_delete: TEdit;
    book_name_delete: TEdit;
    Button1: TButton;
    Button2: TButton;
    book_delete: TADODataSet;
    procedure FormCreate(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button1Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  book_delete: Tbook_delete;
  book_no_temp:string;
  i:integer;

implementation
uses unit3;
{$R *.dfm}

procedure Tbook_delete.FormCreate(Sender: TObject);
begin
    book_no_delete.Text:='';
    book_name_delete.Text:='';
end;

procedure Tbook_delete.Button2Click(Sender: TObject);
begin
    book_no_delete.Text:='';
    book_name_delete.Text:='';
end;

procedure Tbook_delete.Button1Click(Sender: TObject);
begin
      book_delete.Active:=false;
      book_delete.CommandText:='select * from per_book';
      book_delete.Active:=true;
      if (book_no_delete.Text<>'')and(book_name_delete.Text<>'')then
      begin
          if(book_delete.Locate('series',VarArrayOf([book_no_delete.Text]),[loPartialKey])) then
          begin
               with book_delete do
               begin
                   book_no_temp:=fieldbyname('book_no').AsString;
                   delete;
                   active:=false;
               end;
               book_delete.CommandText:='select * from book';
               book_delete.Active:=true;
               book_delete.Locate('book_no',VarArrayOf([book_no_temp]),[loPartialKey]);
               with book_delete do
               begin
                   edit;
                   i:=fieldbyname('book_num').AsInteger;
                   fieldbyname('book_num').AsInteger:=i-1;
                   post;
                   i:=fieldbyname('book_num').AsInteger;
                   active:=false;
                   active:=true;
               end;
               if (i=0) then
               begin
                   with book_delete do
                   begin
                   delete;
                   end;
               end;
               showmessage('已经成功删除这本书。');
          end
          else
               showmessage('该图书馆不存在这本书,请确定是否输入错。');
      end
      else
          showmessage('还没有完全输入数据，请立刻输入。');

end;

end.