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爲什麼此查詢不起作用?我收到錯誤「不是單組功能」。Oracle。將sum()與子查詢相乘。
select sum(stock.stkprice) * (select nation.exchrate from nation where nation.natcode = 'UK') from stock;
是否因爲子查詢可能會返回多個值?它使用主鍵natcode,所以它只應該返回一個單一的匯率。下面是表格。
create table nation
(natcode char(3) not null,
natname char(20),
exchrate number(9,5),
constraint pk_nation primary key (natcode));
create table stock
(stkcode char(3) not null,
stkfirm char(20),
stkprice number(6,2),
stkqty number(8),
stkdiv number(5,2),
stkpe number(5),
natcode char(3),
constraint pk_stock primary key (stkcode),
constraint fk_hasnation foreign key (natcode) references nation(natcode));