Question

如果我将输入调用为3，尝试返回底部3结果的总和。目前它返回的数据集不允许，我该如何解决？

代码看起来像

DELIMITER++

CREATE FUNCTION function1 (input INT) returns INT
BEGIN
DECLARE amount int;

    SET amount = input;

    SELECT SUM(T.C1*Y.C2) 
    FROM Table T, YTable Y 
    WHERE T.ID=Y.TID 
    ORDER BY T.C1*Y.C2 ASC 
    LIMIT amount;

END++

表T（C1，ID）具有值

(20,1), (50,2), (100,3), (110, 4)

YTable Y（C2，TID）具有值

(30, 1), (90, 2), (110, 3), (160,4)

预期输出为20 * 30 + 50 * 90 + 100 * 110 = 16100

Answer 1

使用ROW_NUMBER()确定哪些是最低结果。

WITH cte as (
     SELECT T.C1*Y.C2 as total, 
            ROW_NUMBER() OVER (ORDER BY T.C1*Y.C2) as rn
     FROM Table T
     JOIN YTable Y 
       ON T.ID = Y.TID 
)
SELECT SUM(total)
FROM cte
WHERE rn <= input

Answer 2

使用CONCAT()，prepare和execute构建查询。

sql创建一个通过输入限制的函数

2 个答案: