再delphi前台处理sql语句不认Nz()函数，什么样的函数能像sqlserver里的isnull一样呢

[zcfzcf001]

with adoq do
begin

SQL.Clear;
SQL.Add('select Nz(sum(jhje),0) from jh where gysbh='''+gysbh1+'''');
Open;
Close;
end;

[wwwwb]

select iif(isnull(sum(jhje)),0,sum(jhje)) from jh

[wwwwb]

or
select iif(sum(jhje) is null,0,sum(jhje)) from jh