SQL 格式 $ 和舍入

Question

我正在尝试显示标题、ISBN、成本和类别中图书数量最少的类别，同时还尝试在输出前添加一个“$”作为成本，同时尝试舍入它保留两位小数。

类别示例 =

Technology = 4
Family = 3
Sports = 2
Business = 4

在这种情况下，我希望输出显示体育类别

Select TITLE, ISBN,
Round( '$' + CAST(COST AS VARCHAR(15)) COST, 2),
 CATEGORY
From BOOKS
GROUP By category
HAVING Category = ((Select Min(Category)
From (Select Count(Category) AS Category)
From BOOKS
Group By Category)
;

Answer 1

Oracle 使用|| 进行字符串连接。要获取具有最小计数的类别，您可以使用内联视图，一个获取计数，另一个获取最小计数，join 使用原始表。

select b.TITLE, b.ISBN,
'$' || TO_CHAR(ROUND(b.COST,2)) cost, b.CATEGORY
From BOOKS b
join (select category,count(*) cnt from books group by category) ct
on b.category = ct.category
join (select min(cnt) mincnt 
      from (select count(*) cnt from books group by category)) minct
on ct.cnt = minct.mincnt