--если ID=1 и CURRENCY_ID=2 тогда PERCENT должен быть равен 0
create table test21 (id integer, currency_id integer, percent number
, constraint check_pct check ( (id, currency_id) not in ((1,2)) or nvl(percent,-1) = 0)
)
create table succeeded.

insert into test21 values(1,2,0)
1 rows inserted

insert into test21 values(10,0,1)
1 rows inserted

insert into test21 values(null,2,3)

1 rows inserted

insert into test21 values(1,2,1)

Error starting at line 9 in command:
insert into test21 values(1,2,1)
Error report:
SQL Error: ORA-02290: check constraint (TEST.CHECK_PCT) violated
02290. 00000 -  "check constraint (%s.%s) violated"
*Cause:    The values being inserted do not satisfy the named check
           
*Action:   do not insert values that violate the constraint.

insert into test21 values(1,2,null)

Error starting at line 11 in command:
insert into test21 values(1,2,null)
Error report:
SQL Error: ORA-02290: check constraint (TEST.CHECK_PCT) violated
02290. 00000 -  "check constraint (%s.%s) violated"
*Cause:    The values being inserted do not satisfy the named check
           
*Action:   do not insert values that violate the constraint.