How to resolve "ORA-02290: check constraint (constraint_name) violated" in a merge statement?

Hello Y'all,

I received "ORA-02290: check constraint (PRODUCTION.PROJ_PH_PHASE_NUMBER_CK) violated" after running the following merge statement:

{code }

merge into project_phase target

  using (select distinct project_id, phase_cd from staging_iris

             where project_id is not null) source

  on (target.project_id = source.project_id and target.phase_number = source.phase_cd)

  when not matched then

  insert (target.project_id, target.phase_number)

  values (source.project_id, source.phase_cd)

/

{code }

The following code is excerpted from the script for table project_phase:

{code }

ALTER TABLE PROJECT_PHASE ADD (

  CONSTRAINT PROJ_PH_PHASE_NUMBER_CK