-- I don't need to change this constraint after all, but the Null does seem to work

select CONSTRAINT_NAME,TABLE_NAME,SEARCH_CONDITION   
	from user_constraints 
	where table_name='PEOPLES';

-- job_rank column has allowed values IN ('pd', 'gs', 'ot', 'tp', 'tl', 'up', 'ul')

select unique job_rank from peoples;

-- all records have job_rank=Null

-- original constraint:
PROMPT Creating Check Constraints on 'PEOPLES'
	ALTER TABLE PEOPLES
	ADD (CONSTRAINT AVCON_45475_JOB_R_000 CHECK 
	(JOB_RANK IN ('pd', 'gs', 'ot', 'tp', 'tl', 'up', 'ul')))

-- make a new one with a new name:
PROMPT Creating Check Constraints on 'PEOPLES';
	ALTER TABLE PEOPLES
 	ADD (CONSTRAINT AVCON_45475_JOB_R_001 CHECK 
	(JOB_RANK IN (Null, 'pd', 'gs', 'ot', 'tp', 'tl', 'up', 'ul')))

-- delete the new one:
alter table PEOPLES drop constraint AVCON_45475_JOB_R_001
