查询的一个语句，能这样写吗。错在哪里了。

[hooliu6]

with adoquery1 do
begin
close;
sql.Clear;
sql.Add('select * from cars where "'+combobox1.text+'">a and "'+combobox1.text+'"=b');
parameters.ParamByName('a').Value:=datetimetostr(datetimepicker1.date);
parameters.ParamByName('b').Value:=datetimetostr(datetimepicker2.Date);
open;
end;

查询不出数据，没有错误提示。。

[lhy]

sql.Add('select * from cars where "'+combobox1.text+'">:a and "'+combobox1.text+'"=:b');
参数前加":"

[kaikai_kk]

改成:
'select * from cars where '+combobox1.text+'>:a and '+combobox1.text+'=:b'

简化就是... where Field>:a and Field=:b
又大于,又等于,条件矛盾应该是无数据

[hooliu6]

with adoquery1 do
begin
close;
sql.Clear;
sql.Add('select * from cars where "'+combobox1.text+'">:a and "'+combobox1.text+'"<:b');
parameters.ParamByName('a').Value:=datetimetostr(datetimepicker1.date);
parameters.ParamByName('b').Value:=datetimetostr(datetimepicker2.Date);
open;
end;

呵呵，失误，刚才搞错了，这样搞还是没有查询出数据，，

[hllfl]

delphi =:

[wooden954]

with adoquery1 do
begin
close;
sql.Clear;
sql.Add('select * from cars where '+combobox1.text+'>'':a''
and '+combobox1.text+'='':b''');
parameters.ParamByName('a').Value:=datetimetostr(datetimepicker1.date);
parameters.ParamByName('b').Value:=datetimetostr(datetimepicker2.Date);
open;
end;

a b 都是时间参数，那么在替换参数时应该在参数左右两边加引号，而不是在你在ComboBox所表示的列名左右加引号

[goease]

楼上正解，注意在用到字符串和日期时，只有值是需要引号的，字段名并不需要

[simonhehe]

  with adoquery1 do
begin
  close;
  sql.Clear;
  sql.Add(
    format('select * from cars where %s > :a and %s = :b', [combobox1.text, combobox1.text]);
  );
  parameters.ParamByName('a').Value:= QuotedStr(datetimetostr(datetimepicker1.date));
  parameters.ParamByName('b').Value:= QuotedStr(datetimetostr(datetimepicker2.Date));
  open;

end;