如何在Delphi中修复它

Question

我有一个Dbf表，我需要在该列中插入年和日期，该程序不会产生任何错误，但该列为空

我尝试使用查询SQL查询，但失败了

   procedure TForm1.Button1Click(Sender: TObject);
   var year:string;
   pogr_d:string;
   begin
   pogr_d:='';
   year:='';
   year:=copy(formatdatetime('yyyy',(DateTimePicker1.Date)),1,4);
   Label1.Caption:=year;
   Label2.Caption:=pogr_d;
   if opendialog1.Execute then
   if opendialog1.Filename <> null then
   begin

        TextReader1.FileName := opendialog1.FileName;
        try
              ImportFromText.Execute;
              FDQuery1.Close;
              FDQuery1.Active;
              FDQuery1.SQL.Text:='update g_rabn.dbf set 
    year='+''''+year+'''' +' where year='+''''+'''';
              FDQuery1.ExecSql;

        Except
                  On E : Exception Do
                  ShowMessage(E.Message);
        end;



  end;




  end;

  end.

会发生什么：

我所拥有的：

Answer 1

您确定年份包含空字符串吗？可以为NULL吗？您可以尝试以下sql：

'update g_rabn.dbf set year='+''''+year+'''' +' where coalesce(year,'''')='+''''+''''

Answer 2

您可以使用此代码作为示例。我假设[日期]和[年份]字段为NVARCHAR（4）类型。我还假设您已经设置了数据库连接FConn。

要重现此示例，您将需要一个具有DBGrid1，DateTimePicker1，Edit1，ADOQuery1，ADOQuery2，DataSource1的Form1和两个按钮：Button1插入新记录，而Button2更新现有记录。

通过DataSource1将DBGrid1链接到ADOQuery1。

uses
  ADODB, DB, DateUtils;

type
  TForm1 = class(TForm)
  ...
  private
    { Private declarations }
    FConn: TADOConnection;
    FYear: Integer;
    FMonth: Integer;
    FDay: Integer;
    FYearUpd: String;
  ...

const
  SQL1 = 'INSERT [Dbf] ([Date], [Year]) VALUES (''%s%s'', ''%s'')';
  SQL2 = 'UPDATE [Dbf] SET [Year] = ''%s'' WHERE Year = ''%s''';

procedure TForm1.FormCreate(Sender: TObject);
begin
  // FConn connection initialization

  ADOQuery1.Connection := FConn;
  ADOQuery2.Connection := FConn;
  ADOQuery1.SQL.Text := 'SELECT * FROM Dbf';
  ADOQuery1.Open;
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  FYear := YearOf(DateTimePicker1.Date);
  FMonth := MonthOf(DateTimePicker1.Date);
  FDay := DayOf(DateTimePicker1.Date);

  // Inserting a new record.
  ADOQuery2.SQL.Text := Format(SQL1, [IntToStr(FDay), IntToStr(FMonth), IntToStr(FYear)]);
  ADOQuery2.ExecSQL;

  // Refreshing the DBGrid.
  ADOQuery1.Close;
  ADOQuery1.Open;
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  FYear := YearOf(DateTimePicker1.Date);
  FYearUpd := Trim(Edit1.Text);

  // Updating existing records.
  ADOQuery2.SQL.Text := Format(SQL2, [FYearUpd, IntToStr(FYear)]);
  ADOQuery2.ExecSQL;

  // Refreshing the DBGrid.
  ADOQuery1.Close;
  ADOQuery1.Open;
end;