一个简单一问题,在DELPHI中有没有宏替换的函数?(50分)

procedure Tifleave.BitBtn1Click(Sender: TObject);
begin
case RadioGroup1.ItemIndex of
0:WhyLeft:='L';
1:WhyLeft:='D';
2:WhyLeft:='F';
end;
LeftDate:=DateToStr(datetimepicker1.Date);
OtherThing:=Memo1.Text;
with Frm_Datain1.ADOCommand1 do begin
CommandText:='insert into salarout select *,'+LeftDate+' as levdate,'+WhyLeft+' as whylev from salaryin where no=:NoParam';
Parameters[0].Value:=Frm_Datain1.DBEdit1.Text;
Execute;
CommandText:='delete salaryin where no=:NoParam';
Parameters[0].Value:=Frm_Datain1.DBEdit1.Text;
Execute;
end;
Frm_Datain1.AdoDataset1.Requery;
Frm_Datain1.bAppend:=false;
end;
几个变量在前面都已经定义;
但这句有错CommandText:='insert into salarout select *,'+LeftDate+' as levdate,'+WhyLeft+' as whylev from salaryin where no=:NoParam';
比如当WhyLeft='L'时,报错:列名'L'无效,表结构是没错的,
我故意换成CommandText:='insert into salarout select *,'+LeftDate+' as levdate,'+'''L'' as whylev from salaryin where no=:NoParam';
就没错!为什么会这样啊!

哦不好意思看的太快了，呵呵，你可以这样，
const
SQL = 'select a, b ,%s from abc';

然后
LeftDate := 'L';
str := format(SQL, [L]);
xxx.SQL.Text := str;
xxx.Open;

多谢kKYY,呵呵,麻烦帮我看一下报错原因!

'insert into salarout select *,'+LeftDate+' as levdate,'+WhyLeft+' as whylev from salaryin where no=:NoParam'
生成的是：
'insert into salarout select *,02/11/19 as levdate,L as whylev from salaryin where no=:NoParam'
知道错在哪了吗？ （我敢打赌你的levdate也不会对）

谢Another_eYes:
levdate 是对的,我说过CommandText:='insert into salarout select *,'+LeftDate+' as levdate,'+'''L'' as whylev from salaryin where no=:NoParam';
就没错!为什么会这样啊!

在Form上再放一个memo,把你生成后的commandtext作为memo.text输出，看看出现的是什么，
然后再查错！
另外，Another_eYes说的没错，可能是你的系统日期格式有所不同，所以能在另一种情况下骗过
SQL，让它以为是对的！

''L''
你这里的 'L' 是个常量，当然不会错！！！

到底是怎么回事?字段都是字符型的呀!

to beadly:
你想要的结果应当是：
insert into salarout select *,'02/11/19' as levdate,'L' as whylev from salaryin where no=:NoParam 吧
而你现在得到的是：
insert into salarout select *,02/11/19 as levdate,L as whylev from salaryin where no=:NoParam
所以你的语句应当写成：
CommandText:='insert into salarout select *,'''+LeftDate+''' as levdate,'''+WhyLeft+''' as whylev from salaryin where no=:NoParam';

to dlnew:
不是他的系统日期格式不同而“骗过”SQL， 根本没骗， 只是SQL认为02/11/19是个数学表达式： 2除以11再除以19
所以最后获得的levdate字段是个浮点数字段而不会是日期字段（所以我说levdate肯定不对）

太多谢各位了........