I saw a funny one today. I’ll paraphrase:
select * from table_x where upper(acct_number) = '876876' or upper(acct_number) = '826531';
1. Obviously turns off any indexes on acct_number (unless they had a function based index).
2. Looks like they are probably storing numeric data in a character data type (or implicitly converting a number to character string).
3. Not using bind variables so they are not helping themselves from a parsing standpoint.
4. Finally, they’re making darn sure they take care of any mixed case numbers!
(by the way, those lower case numbers cause me problems all the time)