Delphi中ADOQuery删除多表中的数据问题

Posted 2021-05-21 码农的笔记

-------------------Delphi 7----

-----本次测试没有用到第三方控件----

ADOquery的多表关联，如果直接ADOquery1.delete；会删除多个表的数据；

如果要删除资料，请另行写SQL语句，有人说把这个SQL语句放在ADOquery1.BeforeDelete中；感觉太麻烦；

这在项目中怎么能行！不好控制啊，删除的统一放一起多好；个人感觉放一起好点，哈哈。

 

-----------

本人测试的这个例子，为的是写在基类中，才这么测试的！

------------------------

ADOConnection1.ConnectionString 已清空，请自行配置；

----------------------

------------MS SQL Server 2008--------中---开始--

1.表：StudentInfo

CREATE TABLE [dbo].[StudentInfo](
[StudentID] [varchar](10) NOT NULL,
[StudentName] [varchar](20) NOT NULL,
CONSTRAINT [PK_StudentInfo] PRIMARY KEY CLUSTERED
(
[StudentID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

 

2.表CourseScore：

CREATE TABLE [dbo].[CourseScore](
[CourseNo] [varchar](10) NOT NULL,
[StudentID] [varchar](10) NOT NULL,
[score] [int] NOT NULL,
CONSTRAINT [PK_CourseScore] PRIMARY KEY CLUSTERED
(
[CourseNo] ASC,
[StudentID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

 

----插入数据：

insert into dbo.StudentInfo values(\'A0001\',\'小马\'),(\'A0002\',\'小黑\'),(\'A0003\',\'小白\'),(\'A0004\',\'小二\')
insert into dbo.CourseScore values(\'C001\',\'A0001\',60),(\'C001\',\'A0002\',63),(\'C001\',\'A0003\',96),(\'C001\',\'A0004\',81)
insert into dbo.CourseScore values(\'C002\',\'A0001\',67),(\'C002\',\'A0002\',65),(\'C002\',\'A0003\',88),(\'C002\',\'A0004\',78)

 

------------------------------MS SQL Server 2008--------中------结束----

 

Delphi Code:

---------Unit---开始

unit Unit1;

interface

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

type
TOperateTable=class(TObject)
TableName:string;
UniqueKey:string;//Field之间请用英文状态下的分号隔开
end;

TForm1 = class(TForm)
ADOQuery1: TADOQuery;
Button1: TButton;
Button2: TButton;
Button3: TButton;
ComboBox1: TComboBox;
DBGrid1: TDBGrid;
DBGrid2: TDBGrid;
DataSource1: TDataSource;
DataSource2: TDataSource;
ADOQuery2: TADOQuery;
ADOConnection1: TADOConnection;
ADOQuery2courseNo: TStringField;
ADOQuery2StudentID: TStringField;
ADOQuery2Studentname: TStringField;
ADOQuery2score: TIntegerField;
Button4: TButton;
Memo1: TMemo;
procedure Button1Click(Sender: TObject);
procedure FormShow(Sender: TObject);
procedure FormDestroy(Sender: TObject);
procedure Button4Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure Button2Click(Sender: TObject);
procedure Button3Click(Sender: TObject);
private
FQueryInfo:TStringList;
{ Private declarations }
public
function QueryAdd(DBGridName:string):Boolean;
function QueryDelete(DBGridName:string):Boolean;
{ Public declarations }
end;

var
Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
//
end;

function TForm1.QueryAdd(DbgridName: string): Boolean;
begin
//
end;

procedure TForm1.FormShow(Sender: TObject);
var
ss:TOperateTable;
begin
ComboBox1.ItemIndex:=0;
FQueryInfo:=TStringList.Create;

//////////////DBGrid1的真实操作的表
ss:=TOperateTable.Create;
ss.TableName:=\'StudentInfo\';
ss.UniqueKey:=\'StudentID\';//唯一索引
FQueryInfo.AddObject(\'DBGrid1\',ss);
///////////////////

ss:=TOperateTable.Create;
ss.TableName:=\'CourseScore\';//DBGrid2的真实操作的表
ss.UniqueKey:=\'courseNo;StudentID\';//唯一索引
FQueryInfo.AddObject(\'DBGrid2\',ss);

end;

procedure TForm1.FormDestroy(Sender: TObject);
var
i:Integer;
begin
if FQueryInfo<>nil then //自己创建的就要自己释放
begin
if FQueryInfo.Count>0 then
begin
for i:=0 to FQueryInfo.Count-1 do
begin
FQueryInfo.Objects[i].Free;
end;
end;
FQueryInfo.Clear;
FQueryInfo.Free;
end;
end;

procedure TForm1.Button4Click(Sender: TObject);
begin
//刷新两个数据集
(DBGrid1.DataSource.DataSet as TADOQuery).Close;
(DBGrid1.DataSource.DataSet as TADOQuery).Open;
(DBGrid2.DataSource.DataSet as TADOQuery).Close;
(DBGrid2.DataSource.DataSet as TADOQuery).Open;
end;

procedure TForm1.FormCreate(Sender: TObject);
begin
(DBGrid1.DataSource.DataSet as TADOQuery).SQL.Text:=\'select * from dbo.StudentInfo \';
(DBGrid2.DataSource.DataSet as TADOQuery).SQL.Text:=\'select a.courseNo,a.StudentID,b.Studentname,a.score from dbo.CourseScore a inner join dbo.StudentInfo b on a.StudentID=b.StudentID\';
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
//
end;

procedure TForm1.Button3Click(Sender: TObject);
begin
//只想删除CourseScore中的某笔数据但是会把 StudentInfo表的数据也删除了
QueryDelete(ComboBox1.Text); //ComboBox1来指定删除那个DBGrid的数据
end;

function TForm1.QueryDelete(DBGridName: string): Boolean;
var
vQuery:TADOQuery;
vTableInfo:TOperateTable;
vTableWhere,vstr:string;
vstrList:TStringList;
i:Integer;
vDBGrid:TDBGrid;
begin
Result:=False;
if FQueryInfo.Count=0 then //用到项目中要判断FQueryInfo
Exit;
vDBGrid:=TDBGrid(FindComponent(DBGridName));
if vDBGrid=nil then
Exit;
try
vstrList:=TStringList.Create;
vTableInfo:=TOperateTable(FQueryInfo.Objects[FQueryInfo.IndexOf(DBGridName)]);

vQuery:=TADOQuery.Create(Self);
vstrList.Delimiter:=\';\';
vstrList.DelimitedText:=vTableInfo.UniqueKey;
if vstrList.Count >0 then
begin
for i:=0 to vstrList.Count-1 do
begin
vstr:=vstrList.Strings[i];
//MSSQL数据库会自动的类型转换，为此就算是数字类型的也按字符串类型处理！
//vTableWhere:=vTableWhere+\' and \'+vstr+\'=\'\'\'+(vDBGrid.DataSource.DataSet as TADOQuery).fieldbyname(vstr).AsString+\'\'\'\';//这个不好，最好按下面这句
vTableWhere:=vTableWhere+\' and \'+vstr+\'=\'+Quotedstr((vDBGrid.DataSource.DataSet as TADOQuery).fieldbyname(vstr).AsString);
end;
Delete(vTableWhere,1,5);
vQuery.Connection:=ADOConnection1;
vQuery.SQL.Text:=\' Delete from \'+vTableInfo.TableName +\' Where \'+vTableWhere;
Memo1.Lines.Add(vQuery.SQL.Text);
vQuery.Prepared:=True;
vQuery.ExecSQL;

(vDBGrid.DataSource.DataSet as TADOQuery).Close;
(vDBGrid.DataSource.DataSet as TADOQuery).Open ;
end;

finally
vstrList.Free;
vQuery.Free;
end;
end;

end.

 

-----------Unit---结束-----------------------------------------------------------

 

-------------Form开始---------

object Form1: TForm1
Left = 667
Top = 298
Width = 443
Height = 538
Caption = \'Form1\'
Color = clBtnFace
Font.Charset = DEFAULT_CHARSET
Font.Color = clWindowText
Font.Height = -11
Font.Name = \'MS Sans Serif\'
Font.Style = []
OldCreateOrder = False
OnCreate = FormCreate
OnDestroy = FormDestroy
OnShow = FormShow
PixelsPerInch = 96
TextHeight = 13
object Button1: TButton
Left = 16
Top = 328
Width = 75
Height = 25
Caption = \'新增\'
TabOrder = 0
OnClick = Button1Click
end
object Button2: TButton
Left = 16
Top = 360
Width = 75
Height = 25
Caption = \'修改\'
TabOrder = 1
OnClick = Button2Click
end
object Button3: TButton
Left = 232
Top = 336
Width = 75
Height = 25
Caption = \'删除\'
TabOrder = 2
OnClick = Button3Click
end
object ComboBox1: TComboBox
Left = 56
Top = 304
Width = 129
Height = 21
Style = csDropDownList
ImeName = \'中文(简体) - 搜狗拼音输入法\'
ItemHeight = 13
TabOrder = 3
Items.Strings = (
\'DBGrid1\'
\'DBGrid2\')
end
object DBGrid1: TDBGrid
Left = 24
Top = 16
Width = 320
Height = 120
DataSource = DataSource1
ImeName = \'中文(简体) - 搜狗拼音输入法\'
TabOrder = 4
TitleFont.Charset = DEFAULT_CHARSET
TitleFont.Color = clWindowText
TitleFont.Height = -11
TitleFont.Name = \'MS Sans Serif\'
TitleFont.Style = []
end
object DBGrid2: TDBGrid
Left = 24
Top = 152
Width = 320
Height = 120
DataSource = DataSource2
ImeName = \'中文(简体) - 搜狗拼音输入法\'
TabOrder = 5
TitleFont.Charset = DEFAULT_CHARSET
TitleFont.Color = clWindowText
TitleFont.Height = -11
TitleFont.Name = \'MS Sans Serif\'
TitleFont.Style = []
end
object Button4: TButton
Left = 352
Top = 136
Width = 65
Height = 25
Caption = \'Button4\'
TabOrder = 6
OnClick = Button4Click
end
object Memo1: TMemo
Left = 16
Top = 400
Width = 377
Height = 97
ImeName = \'中文(简体) - 搜狗拼音输入法\'
Lines.Strings = (
\'Memo1\')
ScrollBars = ssBoth
TabOrder = 7
end
object ADOQuery1: TADOQuery
Connection = ADOConnection1
Parameters = <>
SQL.Strings = (
\'select * from dbo.StudentInfo \')
Left = 224
Top = 64
end
object DataSource1: TDataSource
DataSet = ADOQuery1
Left = 152
Top = 72
end
object DataSource2: TDataSource
DataSet = ADOQuery2
Left = 112
Top = 200
end
object ADOQuery2: TADOQuery
Connection = ADOConnection1
CursorType = ctStatic
Parameters = <>
SQL.Strings = (

\'select a.courseNo,a.StudentID,b.Studentname,a.score from dbo.Co\' +
\'urseScore a inner join dbo.StudentInfo b on a.StudentID=b.Studen\' +
\'tID\')
Left = 184
Top = 192
object ADOQuery2courseNo: TStringField
FieldName = \'courseNo\'
Size = 10
end
object ADOQuery2StudentID: TStringField
FieldName = \'StudentID\'
Size = 10
end
object ADOQuery2Studentname: TStringField
FieldName = \'Studentname\'
end
object ADOQuery2score: TIntegerField
FieldName = \'score\'
end
end
object ADOConnection1: TADOConnection
LoginPrompt = False
Provider = \'SQLOLEDB.1\'
Left = 304
Top = 176
end
end

----------------Form结束--------------