如何在 SQL 服务器中获取字符串形式的值

Question

我有一个 table tbl_Marks:

Std_id  | sub_id  |  term_I   | term_2
--------+---------+-----------+-------
std_1   | 1       |   40      | 50
std_1   | 2       |   30      | 40
std_1   | 3       |   20      | 30
std_1   | 4       |   10      | 50

std_2   | 1       |   50      | 50
std_2   | 2       |   50      | 50
std_2   | 3       |   50      | 50
std_2   | 4       |   50      | 50

我怎样才能得到这样的结果：

Std_id  | sub_id  |  term_I   | term_2 | total  | status | PROMOTION_status
--------+---------+-----------+--------+--------+--------+------------------
std_1   | 1       |   40      | 50     | 90     | PASS   | REPEATER
std_1   | 2       |   30      | 40     | 70     | PASS   | REPEATER
std_1   | 3       |   20      | 20     | 40     | FAIL   | REPEATER
std_1   | 4       |   10      | 50     | 60     | PASS   | REPEATER

注意：如果总值小于任何 sub_id

的 50

std_2   | 1       |   50      | 50     | 100    | PASS   | PROMOTED
std_2   | 2       |   50      | 50     | 100    | PASS   | PROMOTED
std_2   | 3       |   50      | 50     | 100    | PASS   | PROMOTED
std_2   | 4       |   50      | 50     | 100    | PASS   | PROMOTED

注意：如果总值大于 50 或等于每个 sub_id

请帮忙！

Answer 1

使用CASE。

 select t.*,
        t.term_I + t.term_2 as total,
        case when t.term_I + t.term_2 >= 50 then 'pass' else 'fail' end as status,
        case when t.std_id = 'std_2' then 'PRMOTED' else 'REAPEATER' end as promotion_status
 from tbl_marks t

Answer 2

以下 SQL Select 语句可以提供帮助 除了 SQL CTE expression 你还可以使用 subselect 语句 但是这个查询的主要技巧是使用 MIN aggregation function with Partition by 子句 这可以帮助您检查该学生的分数是否低于 50，如果是，它会将该学生的所有记录设为重复状态

;with cte as (
select  
*, 
term_1 + term_2 as total
from tbl_Marks
)
select
*,
case when (term_1 + term_2) >= 50 then 'PASS' else 'FAIL' end as status,
case when (
min(total) over (partition by Std_id)
) >= 50 then 'PROMOTED' else 'REPEATER' end as PROMOTION_status
from cte

希望对您有所帮助，