Question

Delphi使用动态sql语句时出现错误

procedure TForm1.Button3Click(Sender: TObject);
begin
Name:=Edit1.Text;
Query1.Close;
Query1.SQL.Clear;
Query1.SQL.Add('select * from animals.dbf');
Query1.SQL.Add('where name=:name');
Query1.ParamByName('name').AsString:=Name;

if Query1.RecordCount=0 then
ShowMessage('没有这条记录')
else begin
Query1.Close;
Query1.SQL.Clear;

Query1.SQL.Add('update animals.dbf');
query1.SQL.Add('set name="New Name"');
Query1.SQL.Add('where name=:name');
Query1.ParamByName('name').AsString:=Name;
Query1.ExecSQL;

Query1.Close;
Query1.SQL.Clear;
Query1.SQL.Add('select * from animals.dbf');
Query1.Open;
end;
end;

end.
上面全局变量忘写了
var
Name:string;

Answer 1

错误提示数据集没有打开，你改为下面的代码看看
procedure TForm1.Button3Click(Sender: TObject);
begin
Name:=Edit1.Text;
Query1.Close;
Query1.SQL.Clear;
Query1.SQL.Add('select * from animals.dbf');
Query1.SQL.Add('where name=:name');
Query1.ParamByName('name').AsString:=Name;

Query1.open;//这里应该添加一句，打开数据集
if Query1.RecordCount=0 then
ShowMessage('没有这条记录')
else begin
Query1.Close;
Query1.SQL.Clear;

Query1.SQL.Add('update animals.dbf');
query1.SQL.Add('set name="New Name"');
Query1.SQL.Add('where name=:name');
Query1.ParamByName('name').AsString:=Name;
Query1.ExecSQL;

Query1.Close;
Query1.SQL.Clear;
Query1.SQL.Add('select * from animals.dbf');
Query1.Open;
end;
end;

end.

Answer 2

Query1.SQL.Add('select * from animals.dbf');
Query1.SQL.Add('where name=:name');
这样连接组合SQL时，第一句和第二句中间的空格，
第二：Query1.ParamByName('name').AsString:=Name;
给绑定变量赋值也不是这样吧！
试试下面这句话Query1.Parameters.ParamByName('name').Value:=Name
第三：主意绑定变量和局部变量最好不要同名，