The ASCII function returns the NUMBER code that represents the specified character.ASCII( single_character )

SELECT ASCII(\'A\') FROM dual;
Output:A

The CHR function is the opposite of the ascii function. It returns the character based on the NUMBER code.
CHR( number_code )

SELECT CHR(9) FROM dual;
Output:TAB

记录这个的原因是因为，遇到一客户问题，发现系统里的lot number中有空格似的字符，但是使用下边的query，又查不出来
select * from mtl_lot_numbers where lot_number<> ltrim(rtrim(lot_number));
最后才发现是因为lot number的中是有Tab字符（trim不会处理tab字符）。可以使用下边的query来查询确认
select *
from apps.mtl_lot_numbers
WHERE organization_id=207
and inventory_item_id=606
and lot_number like \'S00001%\'|| CHR(9);