DBLookupCombobox实现下拉联动

USE [his_mz]
GO
/****** Object:  Table [dbo].[City]    Script Date: 2018-8-19 23:04:00 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[City](
    [code] [varchar](10) NOT NULL,
    [name] [varchar](50) NOT NULL,
    [province] [varchar](10) NOT NULL,
    [other] [varchar](50) NULL,
 CONSTRAINT [PK_City] PRIMARY KEY CLUSTERED 
(
    [code] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]

GO
SET ANSI_PADDING OFF
GO
/****** Object:  Table [dbo].[district]    Script Date: 2018-8-19 23:04:00 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[district](
    [code] [varchar](10) NOT NULL,
    [name] [varchar](50) NOT NULL,
    [city] [varchar](10) NOT NULL,
    [other] [varchar](50) NULL
) ON [PRIMARY]

GO
SET ANSI_PADDING OFF
GO
/****** Object:  Table [dbo].[province]    Script Date: 2018-8-19 23:04:00 ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
SET ANSI_PADDING ON
GO
CREATE TABLE [dbo].[province](
    [code] [varchar](10) NOT NULL,
    [name] [varchar](50) NOT NULL,
    [other] [varchar](50) NULL
) ON [PRIMARY]

GO
SET ANSI_PADDING OFF
GO
INSERT [dbo].[City] ([code], [name], [province], [other]) VALUES (N‘c1001‘, N‘北京市‘, N‘1001‘, NULL)
GO
INSERT [dbo].[City] ([code], [name], [province], [other]) VALUES (N‘c1002‘, N‘上海市‘, N‘1001‘, NULL)
GO
INSERT [dbo].[City] ([code], [name], [province], [other]) VALUES (N‘c1003‘, N‘天津市‘, N‘1001‘, NULL)
GO
INSERT [dbo].[City] ([code], [name], [province], [other]) VALUES (N‘c1004‘, N‘重庆市‘, N‘1001‘, NULL)
GO
INSERT [dbo].[City] ([code], [name], [province], [other]) VALUES (N‘c1005‘, N‘广州市‘, N‘1002‘, NULL)
GO
INSERT [dbo].[City] ([code], [name], [province], [other]) VALUES (N‘c1006‘, N‘深圳市‘, N‘1002‘, NULL)
GO
INSERT [dbo].[City] ([code], [name], [province], [other]) VALUES (N‘c1007‘, N‘珠海市‘, N‘1002‘, NULL)
GO
INSERT [dbo].[City] ([code], [name], [province], [other]) VALUES (N‘c1008‘, N‘南宁市‘, N‘1003‘, NULL)
GO
INSERT [dbo].[City] ([code], [name], [province], [other]) VALUES (N‘c1009‘, N‘玉林市‘, N‘1003‘, NULL)
GO
INSERT [dbo].[district] ([code], [name], [city], [other]) VALUES (N‘d1001‘, N‘越秀区‘, N‘c1005‘, NULL)
GO
INSERT [dbo].[district] ([code], [name], [city], [other]) VALUES (N‘d1002‘, N‘荔湾区‘, N‘c1005‘, NULL)
GO
INSERT [dbo].[district] ([code], [name], [city], [other]) VALUES (N‘d1003‘, N‘天河区‘, N‘c1005‘, NULL)
GO
INSERT [dbo].[district] ([code], [name], [city], [other]) VALUES (N‘d1004‘, N‘海珠区‘, N‘c1005‘, NULL)
GO
INSERT [dbo].[district] ([code], [name], [city], [other]) VALUES (N‘d1005‘, N‘黄浦区‘, N‘c1005‘, NULL)
GO
INSERT [dbo].[district] ([code], [name], [city], [other]) VALUES (N‘d1006‘, N‘萝岗区‘, N‘c1005‘, NULL)
GO
INSERT [dbo].[district] ([code], [name], [city], [other]) VALUES (N‘d1007‘, N‘芳村区‘, N‘c1005‘, NULL)
GO
INSERT [dbo].[district] ([code], [name], [city], [other]) VALUES (N‘d1008‘, N‘白云区‘, N‘c1005‘, NULL)
GO
INSERT [dbo].[district] ([code], [name], [city], [other]) VALUES (N‘d1009‘, N‘花都区‘, N‘c1005‘, NULL)
GO
INSERT [dbo].[district] ([code], [name], [city], [other]) VALUES (N‘d1010‘, N‘增城区‘, N‘c1005‘, NULL)
GO
INSERT [dbo].[district] ([code], [name], [city], [other]) VALUES (N‘d1011‘, N‘从化区‘, N‘c1005‘, NULL)
GO
INSERT [dbo].[province] ([code], [name], [other]) VALUES (N‘1001‘, N‘直辖市‘, NULL)
GO
INSERT [dbo].[province] ([code], [name], [other]) VALUES (N‘1002‘, N‘广东省‘, NULL)
GO
INSERT [dbo].[province] ([code], [name], [other]) VALUES (N‘1003‘, N‘广西壮族自治区‘, NULL)
GO

procedure TForm2.FormCreate(Sender: TObject);
begin
  //初始化数据集信息
  qryProvince.Close;
  qryCity.Close;
  qryDistrict.Close;

  qryProvince.SQL.Text := ‘select * from province‘;
  qryCity.SQL.Text := ‘select * from city‘;
  qryDistrict.SQL.Text := ‘select * from district‘;

  qryProvince.Open;
  qryCity.Open;
  qryDistrict.Open;

  //打开数据集
  qryProvince.Open;
  qryCity.Open;
  qryDistrict.Open;

  //初始化DBLookupcombobox
  qryCity.Filtered := False;
  qryCity.Filter := ‘code=‘+QuotedStr(‘‘);
  qryCity.Filtered := True;

  qryDistrict.Filtered := False;
  qryDistrict.Filter := ‘code=‘+QuotedStr(‘‘);
  qryDistrict.Filtered := True;
end;

procedure TForm2.cbProvinceCloseUp(Sender: TObject);
var
  keycode: string;
begin
  if cbProvince.Text=EmptyStr then
    keycode := EmptyStr
  else
    keycode := cbProvince.KeyValue; //关键是keyvalue,keyvalue的值来自于keyField，可以在属性面板设置keyFiled

  //使用filter过滤，只显示Province=keycode的数据集
  qryCity.Filtered := False;
  qryCity.Filter := ‘Province=‘+QuotedStr(keycode);
  qryCity.Filtered := True;

  //清除城市下拉框已选的值
  cbCity.KeyValue := ‘‘;
  cbDistrict.KeyValue := ‘‘;
end;

procedure TForm2.cbCityCloseUp(Sender: TObject);
var
  keycode: string;
begin
  if cbCity.Text=EmptyStr then                
    keycode := EmptyStr
  else
    keycode := cbCity.KeyValue;
  //使用filter过滤，只显示city=keycode的数据集
  qryDistrict.Filtered := False;
  qryDistrict.Filter := ‘city=‘+QuotedStr(keycode);
  qryDistrict.Filtered := True;
  //由于有些城市的区域为空，所以要把DBLookupCombobox的enable设置FALSE，否则会报错
  if qryDistrict.RecordCount=0 then
    cbDistrict.Enabled := False
  else
    cbDistrict.Enabled := True;

  //清除已选择的地区的值
  cbDistrict.KeyValue := ‘‘;
end;