按预定义顺序返回查询结果

Returning query results in predefined order(按预定义顺序返回查询结果)

问题描述

是否可以按预定顺序执行 SELECT 语句，即.选择 ID 7、2、5、9 和 8 并按该顺序返回，仅基于 ID 字段?

Is it possible to do a SELECT statement with a predetermined order, ie. selecting IDs 7,2,5,9 and 8 and returning them in that order, based on nothing more than the ID field?

这两个语句都以相同的顺序返回它们:

Both these statements return them in the same order:

SELECT id FROM table WHERE id in (7,2,5,9,8) 

SELECT id FROM table WHERE id in (8,2,5,9,7)

推荐答案

我不认为这是可能的，但找到了一个 此处的博客条目 似乎是您所追求的类型:

I didn't think this was possible, but found a blog entry here that seems to do the type of thing you're after:

SELECT id FROM table WHERE id in (7,2,5,9,8) 
ORDER BY FIND_IN_SET(id,"7,2,5,9,8");

会给不同的结果

SELECT id FROM table WHERE id in (7,2,5,9,8) 
ORDER BY FIND_IN_SET(id,"8,2,5,9,7");

FIND_IN_SET 返回给它的第二个参数中 id 的位置，因此对于上面的第一种情况，7 的 id 在集合中的位置 1, 2 at 2 等等 - mysql 内部计算出类似

FIND_IN_SET returns the position of id in the second argument given to it, so for the first case above, id of 7 is at position 1 in the set, 2 at 2 and so on - mysql internally works out something like

id | FIND_IN_SET
---|-----------
7  | 1
2  | 2
5  | 3

然后根据FIND_IN_SET的结果进行排序.

then orders by the results of FIND_IN_SET.

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