Question

我创建了一个包含两个CASE列的视图。在最后一列中，我需要得到这些案例字段的总和。代码

CREATE VIEW full_return_data
AS
SELECT  
    return.ID_issuance,
    CASE WHEN DATEDIFF(d, date_of_return, fact_date_of_return) <= 0 THEN 0
         WHEN (fact_date_of_return is NULL) THEN book_local.price
         ELSE DATEDIFF(d,date_of_return, fact_date_of_return) * 30
    END AS fine1,
    CASE WHEN [return].ID_condition > book_exemplar_condition.ID_condition AND [return].ID_condition = 2 THEN book_local.price*0.2
         WHEN [return].ID_condition > book_exemplar_condition.ID_condition AND [return].ID_condition = 3 THEN book_local.price*0.4
         WHEN [return].ID_condition > book_exemplar_condition.ID_condition AND [return].ID_condition = 4 THEN book_local.price*0.6
         WHEN [return].ID_condition > book_exemplar_condition.ID_condition AND [return].ID_condition = 5 THEN book_local.price*0.8
         WHEN (fact_date_of_return is NULL) THEN 0
    END AS fine2,
    (fine1 + fine2) AS fine

FROM book_global INNER JOIN
book_local ON book_local.ID_book_global = book_global.ID_book_global INNER JOIN
book_exemplar ON book_exemplar.ID_book_local = book_local.ID_book_local INNER JOIN
book_exemplar_condition ON book_exemplar_condition.ID_book_exemplar = book_exemplar.ID_book_exemplar INNER JOIN
condition ON condition.ID_condition = book_exemplar_condition.ID_condition INNER JOIN
issuance ON issuance.ID_book_exemplar = book_exemplar.ID_book_exemplar INNER JOIN
[return] ON [return].ID_issuance = issuance.ID_issuance

所以...（fine1 + fine2）AS很好用。我该如何解决这个问题？

Answer 1

一种简单的方法是使其他投影成为子查询的一部分

> df[ order(df),  c(1,1) ] # I want this but without the a.1 column!!!!
   a a.1
4  1   1
3  2   2
8  2   2
1  3   3
5  3   3
6  6   6
7  7   7
10 8   8

另一种方法是实际上对你的两个案例陈述求和，但它可能变得难看

Answer 2

您可以这样做：

SELECT *, (fine1 + fine2) AS fine
from (
    return.ID_issuance,
    CASE WHEN DATEDIFF(d, date_of_return, fact_date_of_return) <= 0 THEN 0
         WHEN (fact_date_of_return is NULL) THEN book_local.price
         ELSE DATEDIFF(d,date_of_return, fact_date_of_return) * 30
    END AS fine1,
    CASE WHEN [return].ID_condition > book_exemplar_condition.ID_condition AND [return].ID_condition = 2 THEN book_local.price*0.2
         WHEN [return].ID_condition > book_exemplar_condition.ID_condition AND [return].ID_condition = 3 THEN book_local.price*0.4
         WHEN [return].ID_condition > book_exemplar_condition.ID_condition AND [return].ID_condition = 4 THEN book_local.price*0.6
         WHEN [return].ID_condition > book_exemplar_condition.ID_condition AND [return].ID_condition = 5 THEN book_local.price*0.8
         WHEN (fact_date_of_return is NULL) THEN 0
    END AS fine2
) X

使用派生表，您可以参考结果集中的sum和其他计算列。

其他选项使用外部申请或CTE。

CASE列的总和

2 个答案: