Question

在我的数据库中，我有一个数据列表

名称值

a/b/c     1
a/b/c/d   1
a/b/c/d/e 1
b/b/c     1
b/b/c/d   2
c/c/d     3
c/c/d/e   4
d/d       5

如果我设置最大长度3我想要

a/b/c  3
b/b/c  3
c/c/d  7
d/d    5

我该怎么做？

CREATE TABLE dataTable (
ID                          BIGINT NOT NULL AUTO_INCREMENT PRIMARY KEY,
Name                        VARCHAR(255),
Value                       INT
) ENGINE=InnoDB;


INSERT INTO dataTable (Name, Value) VALUES ("a/b/c", 1), ("a/b/c/d", 1), ("a/b/c/d/e", 1), ("b/b/c", 1), ("b/b/c/d", 1), ("c/c/d", 1), ("c/c/d/e", 1),  ("d/d", 1);

Answer 1

SELECT LEFT(Name, 5) AS Name, SUM(Value) as TotalValue
    FROM dataTable
    GROUP BY LEFT(Name, 5)

显然，我在我的例子中对5进行了硬编码，但你可以做一个像（2 * MaxLen-1）这样的变量。

Answer 2

select name,
sum(value) as cnt
from
dataTable
group by substring_index(name,'/',3)

折叠给定组的数据

2 个答案: