缺少正確的偏析，表達式丟失，子查詢錯誤

Question

我的數據庫用於包含音樂CD和磁帶的出租中心。

    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
    );

當id_cust ='c1'的客戶借用id_cd ='cd1'的cd時，則bor_cd = 1，而當客戶'c1'返回'cd1'時，我必須在ret_cd中插入值1。

    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))
    );

我必須創建一個觸發器（我不知道如何定義它，但是如果有人知道，我會問一個新問題以接受它的答案） ，每次在ret_cd中插入值1后， 它都會設置bor_cd = 0：

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

然后，我必須向CDS添加一個計算列，以計算最后插入的cd的數量：具有id_cd = cd1的CDS的“ cd1”的數量等於BOR_RET提供的id_cd = cd1的數量。

因此，我想運行以下命令：

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));

我得到這個錯誤：“ 缺少表達 ”。 如果我只運行查詢：選擇quantity_cd ...，我得到的錯誤是：“ 錯誤在第2行：ORA-00907：缺少右括號 ”

或者，更好的是，如何添加此列作為以下內容的區別：

    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;

該線程用於解決計算列的問題，但是如果有人也可以向我解釋如何創建觸發器，我將為其打開一個新線程。

預先謝謝你們。

Answer 1

請在最后一行中注意第二個右括號，但請注意一行。

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)