Question

I have a table called Room and it has columns (ID, type, price…etc)

I want to add constraints for both type and price like:

• if single (s), then price should not be greater than 50,
• if double (d), then price should not be greater than 100, and
• if family (f), then price should not be greater than 150

I tried to add it like this but it’s giving me an error. Not sure how should I write this:

ALTER TABLE ROOM 
ADD (CONSTRAINT CHK_PRICE CHECK (
(TYPE='S' AND PRICE <= 50) AND 
(TYPE='D' AND PRICE <=100) AND 
(TYPE='F' AND PRICE <= 150)));

The error received is:

SQL Error: ORA-02293: cannot validate (xxxx.CHK_PRICE) - check
constraint violated
02293. 00000 - "cannot validate (%s.%s) - check constraint violated"
*Cause:    an alter table operation tried to validate a check constraint to
           populated table that had nocomplying values.
*Action:   Obvious

Answer 1

It sounds like you need to OR together the three conditions, not AND them together. It is impossible for any row to satisfy all three criteria– type cannot simultaneously have a value of S, D, and F. You probably want

ALTER TABLE ROOM 
  ADD (CONSTRAINT CHK_PRICE CHECK (
        (TYPE='S' AND PRICE <=  50) OR -- <-- OR, not AND
        (TYPE='D' AND PRICE <= 100) OR -- <-- OR, not AND
        (TYPE='F' AND PRICE <= 150)));