为何我的TQuery组件连续执行第二次就会出错？

Question

InsertMeterIDQuery.Close;
在这后面你要加入
InsertMeterIDQuery.SQL.ADD(SQL语句）；----->这里不能少！
InsertMeterIDQuery.ParamByName('StartMeterID').AsString:=strStartMeterID;
InsertMeterIDQuery.ParamByName('EndMeterID').AsString:=strEndMeterID;
        
        
        

Answer 1

tempWaterRecord表结构如下：
Field Name  Type  Size  Key  Required filed
ItemID      +            *    yes
MeterID      A      20
MonthNum    S
RotateNum    N
YearNum      S
RecordDate  D
WaterNum    S

Answer 2

InsertMeterIDQuery.Close;
在这后面你要加入
InsertMeterIDQuery.SQL.clear;）；----->这里不能少！
InsertMeterIDQuery.SQL.ADD(SQL语句）；----->这里不能少！
InsertMeterIDQuery.ParamByName('StartMeterID').AsString:=strStartMeterID;
InsertMeterIDQuery.ParamByName('EndMeterID').AsString:=strEndMeterID;
        
        
        

Answer 3

但是我的SQL属性已经事先写在SQL属性中了，怎么还需要动态修改？

Answer 4

        InsertMeterIDQuery.Close;
        InsertMeterIDQuery.Params.Clear();
        InsertMeterIDQuery.Params.CreateParam(ftString,'StartMeterID',ptInput);
        InsertMeterIDQuery.Params.CreateParam(ftString,'EndMeterID',ptInput);
        InsertMeterIDQuery.ParamByName('StartMeterID').AsString:=strStartMeterID;
        InsertMeterIDQuery.ParamByName('EndMeterID').AsString:=strEndMeterID;
        if InsertMeterIDQuery.prepared=false then
            InsertMeterIDQuery.Prepare;
        InsertMeterIDQuery.ExecSQL;
        InsertMeterIDQuery.close;

Answer 5

to blucecat(我真笨～编了20几年了还赶不上盖茨)兄：
还是不行啊。

Answer 6

各位，我把整个单元贴出来，请帮帮忙再看看，谢了。unit ReadMeter;interfaceuses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, Mask, Grids, DBGrids, ComCtrls;type
  TReadMeterForm = class(TForm)
    GroupBox1: TGroupBox;
    Label1: TLabel;
    txtStartMeterID: TEdit;
    Label2: TLabel;
    txtEndMeterID: TEdit;
    GroupBox2: TGroupBox;
    Label3: TLabel;
    txtYearNum: TMaskEdit;
    txtMonthNum: TComboBox;
    Label4: TLabel;
    Button1: TButton;
    Button2: TButton;
    DBGrid1: TDBGrid;
    txtRecordDate: TDateTimePicker;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  ReadMeterForm: TReadMeterForm;implementation
uses
    DataModule,DB;{$R *.DFM}procedure TReadMeterForm.Button1Click(Sender: TObject);
var
    strStartMeterID,strEndMeterID:string;
    SaveChoice:word;
//    intYear,intMonth,intDay:word;
begin
if Button1.caption='开始录入' then  //edit mode
    begin
    //check input
    if txtYearNum.text='' then //invalid input
        begin
        showmessage('请输入年份!');
        txtYearNum.SetFocus();
        exit;
        end;
    if txtMonthNum.text='' then
    begin
        showmessage('请输入月份!');
        txtMonthNum.SetFocus();
        exit;
    end;
(*    if pos(' ',txtRecordDate.text)<>0 then
    begin
        showmessage('请输入日期!');
        txtRecordDate.SetFocus();
        exit;
    end;
*)    //form start and end meterid
    if txtStartMeterID.text='' then
        begin
        //get min meterid in table instead
        with WaterDM.MinMeterIDQuery do
        begin
            if prepared=false then
                prepare;
            open;
            strStartMeterID:=FieldByName('MinMeterID').AsString;
            close;
        end;
        end;
    if txtEndMeterID.text='' then
    begin
        //get min meterid in table instead
        with WaterDM.MaxMeterIDQuery do
        begin
            if prepared=false then
                prepare;
            open;
            strEndMeterID:=FieldByName('MaxMeterID').AsString;
            close;
        end;
    end;    //empty temp table
    with WaterDM.tempWaterRecordTable do
    begin
        if active=true then
            close;
        EmptyTable;
    end;    //generate new data
    with WaterDM do
    begin
        //generate meterid
        InsertMeterIDQuery.Close;
        InsertMeterIDQuery.ParamByName('StartMeterID').AsString:=strStartMeterID;
        InsertMeterIDQuery.ParamByName('EndMeterID').AsString:=strEndMeterID;
        showmessage(InsertMeterIDQuery.SQL.Strings[0]);
        if InsertMeterIDQuery.prepared=false then
            InsertMeterIDQuery.Prepare;
        InsertMeterIDQuery.ExecSQL;
        InsertMeterIDQuery.close;        //generate other data
        UpdatetempWaterRecordQuery.close;
        UpdatetempWaterRecordQuery.ParamByName('MonthNum').AsInteger:=StrToInt(txtMonthNum.text);
        UpdatetempWaterRecordQuery.ParamByName('YearNum').AsInteger:=StrToInt(txtYearNum.text);
        UpdatetempWaterRecordQuery.ParamByName('RecordDate').AsDate:=txtRecordDate.date;
        if UpdatetempWaterRecordQuery.prepared=false then
            UpdatetempWaterRecordQuery.prepare;
        UpdatetempWaterRecordQuery.ExecSQL;
        UpdatetempWaterRecordQuery.close;        //active input grid
        with WaterDM do
        begin
            if tempWaterRecordQuery.prepared=false then
                tempWaterRecordQuery.prepare;
            tempWaterRecordQuery.open;
        end;
    end;    //change button caption
    button1.caption:='结束录入';
    end
else    //save mode
    begin
        //confirm save input
        SaveChoice:=messagedlg('是否保存修改？',mtConfirmation,[mbYes,mbNo],0);
        //save or restore
        if SaveChoice=mrYes then    //save
            begin
                with WaterDM do
                begin
                    //apply updates in query
                    tempWaterRecordQuery.ApplyUpdates;                    MigrateQuery.close;
                    if MigrateQuery.prepared=false then
                        MigrateQuery.prepare;
                    MigrateQuery.ExecSQL;
                    MigrateQuery.close;
                end;
            end
        else    //no save
            begin
            end;
        //empty temp table
        WaterDM.tempWaterRecordTable.EmptyTable();
        //change button caption
        button1.caption:='开始录入';        //close related tables
        if WaterDM.tempWaterRecordQuery.active=true then
            WaterDM.tempWaterRecordQuery.close;
    end;
end;procedure TReadMeterForm.Button2Click(Sender: TObject);
begin
    close;
end;end.

Answer 7

to tikkypeng(千两狂死郎)兄：
我试过了，还是不行。问题根本不出在这里，关键是为什么第二次执行时会出错呢？

Answer 8

是不是这个UpdatetempWaterRecordQuery报错？？

Answer 9

很简单的错误，哈哈，第二次运行后发现字段重复，你进行Query操作前先删除对应记录看看。

Answer 10

也许这里也要创建参数（因为提示是："Invalid Parameter"，一定是参数的问题）
        UpdatetempWaterRecordQuery.close;
        UpdatetempWaterRecordQuery.ParamByName('MonthNum').AsInteger:=StrToInt(txtMonthNum.text);
        UpdatetempWaterRecordQuery.ParamByName('YearNum').AsInteger:=StrToInt(txtYearNum.text);
        UpdatetempWaterRecordQuery.ParamByName('RecordDate').AsDate:=txtRecordDate.date;
        if UpdatetempWaterRecordQuery.prepared=false then
            UpdatetempWaterRecordQuery.prepare;
        UpdatetempWaterRecordQuery.ExecSQL;
        UpdatetempWaterRecordQuery.close;