Of course, it does depend on how the data stored in the table, if the data stored in the MODEL column is in UPPERCASE, then a query you specify in lowercase, will not return any rows. The UPPER function forces the passed variable to be made upper which.

I.e if the data in the table is

MODEL

SUBARU

A. Select style, color, lot_no
From auto
Where model = upper('subaru');

B. Select style, color, lot_no
From auto
Where model = 'subaru';

Query a, will return 1 row and query b, will return no rows returned.

Cheers