unit5.~pas

简单的图书馆查询系统

unit Unit5;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls, Grids, DBGrids, DB, DBTables;

type
  TForm5 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    DBGrid1: TDBGrid;
    Label1: TLabel;
    Edit1: TEdit;
    Label2: TLabel;
    Query1: TQuery;
    Table1: TTable;
    Table2: TTable;
    Table3: TTable;
    DataSource1: TDataSource;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form5: TForm5;

implementation

{$R *.dfm}

procedure TForm5.Button1Click(Sender: TObject);
begin
  close;
end;

procedure TForm5.Button2Click(Sender: TObject);
var
  loc1:boolean;
  loc2:boolean;
  locOp:TLocateOptions;
  currday:TDate;
  days:integer;
begin
  locOp:=[loCaseInsensitive];
    if (edit1.text='')  then
       begin
         showmessage('请输入学号和密码!');
         abort;
       end;
  loc1:=table3.locate('学号',edit1.Text,[]);
  loc2:=table1.locate('学号',edit1.Text,[]);

    if loc2=false then
      begin
        showmessage('无此学号，请查询');
        abort;
      end;

    if loc1=false then
      begin
        showmessage('您还没有借书记录');
        abort;
      end;
  query1.DisableConstraints;
  try
    query1.Close;
    query1.SQL.Clear;
    query1.SQL.Add('select 学号,书号,书名,作者,借阅日期,归还日期 from lent,book  where book.书号=lent.书号 and 学号 like ''%'+trim(Edit1.text)+'%''');
    query1.Open;
  finally
    query1.EnableConstraints;
  end;
  currday:=Date;
  table3.locate('学号',edit1.text,[]);
  days:=table3.FieldByName('归还日期').value-currday;
  if days<0 then
  showmessage('您有过期书，请及时归还');
  edit1.clear;

end;
end.