Oracle 26ai

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create table franck ( val int unique );
insert into franck values (1),(2),(3),(4),(5);

5 rows affected

update franck set val=val+1;

5 rows affected

update franck set val=val+1 where val<3;

ORA-00001: unique constraint (FIDDLE.SYS_C008588) violated on table FIDDLE.FRANCK columns (VAL)
Help: https://docs.oracle.com/error-help/db/ora-00001/