Hi,
I am trying to add constraint, and getting this error.

SQL> alter table ap6.ap_invoices_all
add constraint up_inv_num check(invoice_num = upper invoice_num));


ERROR at line 2:
ORA-02293: cannot enable (AP6.UP_INV_NUM) - check constraint violated

Hintts- The table is already populated. Is this could be the reason?

Thanks in advance.