Oracle SQL assign specific values - sql

Question

So I am working on my coursework and I am sort of stuck as to what to do for this one part. The question is this :
Flatpack(FlatpackID, Name, Colour, Type, UnitPrice)
FlatpackID should be generated by the DBMS
Name has at most 20 characters and should be not null
Colour is optional
Type is one of (Office, Kitchen, Bedroom, General)
UnitPrice should be between 5.00 and 500.00
Okay so the one I need help with is the one that is in bold/italic i.e. "Type is one of (Office, Kitchen, Bedroom, General")
How exactly am I declaring this within my
CREATE TABLE FLATPACK (
);
I asked and I was told it is only allowed those values and nothing else.
Any help would be greatly appreciated! Thanks

Answer 1

One method is a check constraint:
constraint chk_flatpack_type check ( Type in ('Office', 'Kitchen', 'Bedroom', 'General') );
Another option is to set up foreign key constraint to a reference table, and have the reference table only contain these values.

Answer 2

This is one option (having types restricted by a check constraint):
SQL> CREATE TABLE flatpack
2 (
3 flatpackid NUMBER CONSTRAINT pk_fp PRIMARY KEY,
4 name VARCHAR2 (20) NOT NULL,
5 colour VARCHAR2 (20),
6 TYPE VARCHAR2 (20)
7 CONSTRAINT ch_ty CHECK
8 (TYPE IN ('Office',
9 'Kitchen',
10 'Bedroom',
11 'General')),
12 unitprice NUMBER CONSTRAINT ch_pr CHECK (unitprice BETWEEN 5 AND 500)
13 );
Table created.
SQL>
Another, better (why? More flexible, as you can add any type you want, without altering the table) option is to create a table which will be referenced by the TYPE column:
SQL> CREATE TABLE flatpack_type (TYPE VARCHAR2 (20) CONSTRAINT pk_ty PRIMARY KEY);
Table created.
SQL> CREATE TABLE flatpack
2 (
3 flatpackid NUMBER CONSTRAINT pk_fp PRIMARY KEY,
4 name VARCHAR2 (20) NOT NULL,
5 colour VARCHAR2 (20),
6 TYPE VARCHAR2 (20)
7 CONSTRAINT fk_fp_ty REFERENCES flatpack_type (TYPE),
8 unitprice NUMBER CONSTRAINT ch_pr CHECK (unitprice BETWEEN 5 AND 500)
9 );
Table created.
SQL> insert into flatpack_type --> valid values
2 select 'Office' from dual union all
3 select 'Kitchen' from dual union all
4 select 'Bedroom' from dual union all
5 select 'Genral' from dual;
4 rows created.
As of the ID, you could use an identity column (if on 12c or higher), or a standard option for lower versions - a trigger which uses a sequence:
SQL> create sequence seq_fp;
Sequence created.
SQL> create or replace trigger trg_bi_fp
2 before insert on flatpack
3 for each row
4 begin
5 :new.flatpackid := seq_fp.nextval;
6 end;
7 /
Trigger created.
SQL>