Question

我正在尝试查找影片ID返回的迟到次数占总回报的百分比。

我尝试使用with子句创建列，但是不允许在select语句中使用我创建的列

;with totalrentals as
(
select totalrentals = count(*), f.film_id , f.title 
from film f
inner join inventory i on i.film_id = f.film_id 
inner join rental r on r.inventory_id = i.[inventory_id]
group by f.film_id , f.title)
, laterentals as (
select  i.film_id, f.title,r.return_date,duedate=    (r.rental_date+f.rental_duration)
from rental r
inner join inventory i on r.inventory_id = i.inventory_id 
inner join film f on f.film_id = i.film_id 
where r.return_date > (r.rental_date+f.rental_duration)
group by i.film_id,f.title,r.rental_date+f.rental_duration, r.return_date 
),
lr as
(
select Laterentals = count(*), f.film_id , f.title 
from laterentals
inner join film f on laterentals.film_id = f.film_id 
group by f.film_id, f.title 
)
select f.film_id, f.title, lr.laterentals ,tr.totalrentals ,pctlate =     (lr.Laterentals  /tr.totalrentals)*100
from film f 
inner join  lr on lr.film_id = f.film_id 
inner join totalrentals tr on tr.film_id  = f.film_id
inner join inventory i on i.film_id = f.film_id 
inner join rental r on r.inventory_id = i.inventory_id 
group by f.film_id , f.title, lr.laterentals , tr.totalrentals 
order by f.film_id  asc

期望报告输出延迟的回报占总回报的百分比

相反，所有pctlate值= 0

Film_ID   Title               Laterentals     Totalrentals    pctlate
1         ACADEMY DINOSAUR              7               23         0
2         ACE GOLDFINGER                5                7         0

Answer 1

似乎字段lr.Laterentals和tr.totalrentals是INT的类型。乘以1.0并将其转换为DECIMAL

select f.film_id, f.title, lr.laterentals ,tr.totalrentals ,pctlate =     
   CAST( 
       ( (lr.Laterentals * 1.0)  / (tr.totalrentals * 1.0)) * 100 
   AS DECIMAL(18, 3))
from film f

OR：

select f.film_id, f.title, lr.laterentals ,tr.totalrentals ,pctlate =     
   CAST( 
       ( CAST(lr.Laterentals AS DECIMAL(18,3))  / (CAST(tr.totalrentals AS DECIMAL 18,3 )))
           * 100 
   AS DECIMAL(18, 3))
from film f

当数据类型为INT时，您将获得0。如果在除法中仅使用整数，则将获得整数除法。另外，INT没有余数，但是DECIMAL有余数。但是，如果至少有一个数字为decimal或其他类型的余数，则将得到浮点除法

让我展示一个例子：

SELECT (1/2)

输出：0

SELECT ((1 * 1.0) / 2)

输出：0.500000

根据“ with”子句中包含的列进行计算

1 个答案: