missing right parantjesis, missing expression, error on subquery

Question

My database is for a rental centre with music CDs and videotapes.

    create table cds (
    id_cd varchar2(5) pk_cduri primary key,
    artists varchar2(100) not null,
    genre varchar2(20) not null,
    release date not null,
    constraint pk_cds primary key(id_cd)
    );


    create table replenishment(
    id_ap varchar2(5) constraint pk_aprovizionari primary key,
    id_cd varchar2(5),
    quantity_cd number(5,2) default 0,
    price_cd number(5,2) default 0,
    id_cv varchar2(5), 
    cquantity_cv number(5,2) default 0, 
    price_cv number(5,2) default 0,
    data_rep date default sysdate, 
    total_cost as (quantity_cd* price_cd+ quantity_cv* price_cv),
    constraint fk_ap_cd foreign key (id_cd) references  cds,
    constraint fk_ap_cv foreign key (id_cv) references  videotapes
    );

When a customer with id_cust='c1' borrows the cd with id_cd='cd1', then bor_cd=1 and when the customer 'c1' returns the 'cd1' I have to insert value 1 in ret_cd.

    create table bor_ret (
    id int constraint pk_bor_ret primary key,
    id_cust varchar2(5) not null, 
    id_cd varchar2(5),
    bor_cd int default 0,
    ret_cd int default 0,
    id_cv varchar2(5),
    bor_cv int default 0,
    ret_cv int default 0,
    data date default sysdate,
    constraint fk_cd_imp foreign key (id_cd) references cds(id_cd),
    constraint fk_cv_imp foreign key (id_cv) references videotapes(id_cv),
    constraint fk_ab_imp  foreign key (id_cust) references customers,
    constraint ck_imp_cd_value_flag check (bor_cd in (1,0)), 
    constraint ck_imp_cv_value_flag check (bor_cv in (1,0)),
    constraint ck_ret_cd_value_flag check (ret_cd in (1,0)),
    constraint ck_ret_cv_value_flag check (ret_cv in (1,0))
    );

I have to create a trigger (I don't know how to define it, but if someone knows, I will ask a new question to accept it's answer) that sets bor_cd=0 every time after I insert value 1 in ret_cd:

update bor_ret set bor_cd=0 where id_cust=(select id_cust from bor_ret where ret_cd=1);

Then I have to add a computed column to CDS that calculate the quantity of the last cd inserted: the quantity of 'cd1' from CDS which has the id_cd=cd1 is equal with the quantity supplied from BOR_RET where id_cd=cd1.

So, I want to run this command:

alter table cds add quantity as(
 select quantity_cd from replenishment b inner join cds a on a.id_cd=b.id_cd where b.id_cd=
 (select id_cd from cds where rownum=1 order by id_cd desc) -
 (select count(id_cd) from bor_ret d inner join cds c on c.id_cd=d.id_cd where d.id_cd=
 (select id_cd from cds where rownum=1 order by id_cd desc) and d.bor_cd=1));

and I get this error: " missing expression ". If I Run only the query: select quantity_cd... I get the error: " ERROR at line 2: ORA-00907: missing right paranthesis "

Or, better, how can I add this column as differences of:

    select quantity_cd from replenishment where id_cd=(select max(id_cd) from cds) as A

    select count(id_cd) from bor_ret where id_cd=(select max(id_cd) from cds) and bor_cd=1 as B

quantity = A-B;

This thread is for solving the problem with computed column, but if someone can explain me how to create the trigger too I will open a new thread for it.

Thank you guys in advance.

Answer 1

Please note 2nd right parenthesis in the last but one line.

select quantity_cd 
from replenishment b 
inner join cds a on a.id_cd=b.id_cd 
where b.id_cd=
           (select id_cd from cds where rownum=1 order by id_cd desc) - 
           (select count(id_cd) from bor_ret d inner join cds c on c.id_cd=d.id_cd where d.id_cd= (select id_cd from cds where rownum=1 order by id_cd desc)) /* <------ ===*/
    and d.bor_cd=1)