Problem about constraints and validation

Question

hi
I want to add new unique constraint into a table. But current data does not fit to constraint.
My constraint is like this:
ALTER TABLE T_STUDENT ADD
CONSTRAINT UNIQ_STUDENT
UNIQUE (STUDENT_NUMBER, NAME, SURNAME)
DISABLE
VALIDATE;
I want to add constraint and I do not want to update the data. So how can I add constraint without validating current data?

Answer 1

Since you are creating UQ constraint, Oracle will create a UQ index to enforce it. You have to use non-unique index for such a constraint:
SQL> create table t (x int, y int);
Table created.
SQL> insert into t select 1,1 from dual connect by level <= 2;
2 rows created.
SQL> alter table t add constraint t_uq unique(x) enable novalidate;
alter table t add constraint t_uq unique(x) enable novalidate
ERROR at line 1:
ORA-02299: cannot validate (TIM.T_UQ) - duplicate keys found
SQL> alter table t add constraint t_uq unique(x)
  2  using index (create index t_indx on t(x)) enable novalidate;
Table altered.