Question

我想创建一个查询，从一个表中获取名称，然后将其与其他表联系起来，按字母顺序为字母表中的每个字母排序，然后在一个查询中限制为每个字母的n个结果。

所以我不会为每个字母运行26个查询，例如：

SELECT CONCAT_WS(' ',first_name,last_name) AS name FROM encyclopedia WHERE name LIKE "A%" ORDER BY rand() LIMIT 4 
SELECT CONCAT_WS(' ',first_name,last_name) AS name FROM encyclopedia WHERE name LIKE "B%" ORDER BY rand() LIMIT 4 
SELECT CONCAT_WS(' ',first_name,last_name) AS name FROM encyclopedia WHERE name LIKE "C%" ORDER BY rand() LIMIT 4

现在我有：

SELECT 
      e.id,
      CONCAT_WS(' ',first_name,last_name) AS name,
      sg.name AS sub_name, 
      sg.id AS sub_id 
      FROM ( SELECT id,first_name,last_name FROM encyclopedia ORDER BY RAND() LIMIT 4) AS e
      LEFT JOIN encyclopedia_subgenres esub
      ON ( e.id = esub.enc_id )
      LEFT JOIN subgenres sg
      ON ( esub.subgenre_id = sg.id )
      ORDER BY name

然后从php我从结果创建数组：

    Array
(
    [b] => Array
        (
            [2] => Array
                (
                    [name] => B Style
                    [genres] => Array
                        (
                            [26] => Classic
                            [27] => X
                            [29] => Y
                        )

                )

            [7] => Array
                (
                    [name] => Beyonce Giselle Knowles
                    [genres] => Array
                        (
                            [32] => Pop
                        )

                )

        )

    [i] => Array
        (
            [1] => Array
                (
                    [name] => Ivan D
                    [genres] => Array
                        (
                            [27] => R&B
                            [2] => Jazz
                        )

                )

        )

    [m] => Array
        (
            [3] => Array
                (
                    [name] => Maria T
                    [genres] => Array
                        (
                            [26] => Classical
                            [27] => Pop
                            [28] => Dance
                        )

                )

        )

)

但问题是它限制了我只有4个随机结果，可以是同一个字母或任何组合的4个结果。有没有办法做到这一点？

感谢。

Answer 1

我认为sql不是那么灵活 - 但我不确定。你必须为此编写存储过程。

首先创建一个生成此序列的序列：A，B，C，...，Z，A，B，C，...，Z，A，B，C ...... 我们称之为magic_sequence。

然后创建一个临时表，其中包含一个列，init，从魔术序列播种，另一个，count_down，等于4.它应该有26行。我们称之为init_table;

然后编写另一个函数，即acceptance_test

- take a string S with
- decrease count_down of the corresponding row in init_table
- return true if count_down > = 0; otherwise false

现在有一个类似的查询：

SELECT CONCAT_WS(' ',first_name,last_name) AS name FROM encyclopedia WHERE acceptance_test(name) LIMIT 4*26

如果需要，您还必须随机化。

MySQL按字母限制选择名称组，每个字母限制为n个结果

1 个答案: