How to alter a table to add a constraint? - sql

Question

So, the question I have is:
Due to various values entered by users for the status of the facility, this leads
to confusion. The database owner would like to limit the following values
“Open”, “Closed”, “Reserved”, and “Maintenance” to be used for the status of
facility.
My table FACILITY has the following columns:
FACILITYNAME
RATE
STATUS
I tried the following:
ALTER TABLE FACILITY ADD CONSTRAINT FACILITY_STATUS 'Open','Closed','Reserved','Maintenance' FOR STATUS;
I get an error, ORA-00904:invalid identifier
I then tried the following:
ALTER TABLE FACILITY ADD CONSTRAINT STATUS_CHECK CHECK (STATUS IN ('Open','Closed','Reserved','Maintenance'));
It said table altered, but when I tried updating the STATUS column, with 'abc' and 'Open', it says row updated, but nothing happened. I was expecting it to give me a constraint error for 'abc', and updating it to 'Open'.

Answer 1

Strange, for me it is working as expected:
CREATE TABLE FACILITY (
FACILITYNAME VARCHAR2(100),
RATE INTEGER,
STATUS VARCHAR2(20));
Table created.
INSERT INTO FACILITY VALUES ('f1', 1, 'Open');
1 row created.
ALTER TABLE FACILITY ADD CONSTRAINT STATUS_CHECK CHECK (STATUS IN ('Open','Closed','Reserved','Maintenance'));
Table altered.
UPDATE FACILITY SET STATUS = 'abc';
ORA-02290: check constraint (XXX.STATUS_CHECK) violated
Maybe verify the status of the constraint:
SELECT CONSTRAINT_NAME, STATUS, DEFERRABLE, DEFERRED
FROM USER_CONSTRAINTS
WHERE TABLE_NAME = 'FACILITY';
+------------------------------------------------+
|CONSTRAINT_NAME|STATUS |DEFERRABLE |DEFERRED |
+------------------------------------------------+
|STATUS_CHECK |ENABLED|NOT DEFERRABLE|IMMEDIATE|
+------------------------------------------------+
Also note, unless you give clause VALIDATE in your ALTER TABLE the constraint does not check existing values! By default only new and updated values are affected by the constraint.

Answer 2

As #KaushikNayak suggested try adding check constraint:
ALTER TABLE FACILITY ADD CONSTRAINT check_status CHECK (FACILITY_STATUS IN ('Open','Closed','Reserved','Maintenance'));
Otherwise, Column level constraint must use another column:
a column-level constraint
Column-level constraints refer to a single column in the table and do not specify a column name (except check constraints). They refer to the column that they follow.
I suggest you create table FACILITY_STATUS with column STATUS as Primary key and insert the values.
Then add constraint to FACILITY table STATUS column using FACILITY_STATUS(STATUS) as foreign key