Use sysdate-1 para subtrair um dia da data do sistema.
select sysdate, sysdate -1 from dual;
Resultado:
SYSDATE SYSDATE-1
-------- ---------
22-10-13 21-10-13
select sysdate, sysdate -1 from dual;
SYSDATE SYSDATE-1
-------- ---------
22-10-13 21-10-13
