Question

我遇到了问题并且已经有一些类似的问题，但它们并没有解决我的问题。

我有几家酒店和图片。图片以数字排序。我想要所有酒店和数字最少的图片。

当我尝试跟踪查询时，我得到正确的顺序：

SELECT s25.entry_id AS id, 
s25.value AS title, 
s35.file AS picture, 
s86.value AS picture_sort 
FROM sym_entries_data_25 AS s25 
LEFT JOIN sym_entries_data_34 AS s34 ON (s25.entry_id = s34.relation_id)     
LEFT JOIN sym_entries_data_35 AS s35 ON (s34.entry_id = s35.entry_id) 
LEFT JOIN sym_entries_data_86 AS s86 ON (s34.entry_id = s86.entry_id) 
ORDER BY s86.value

我将获得数组

[0] => Array
    (
        [id] => 243
        [title] => Hotel
        [picture] => louis2.jpg
        [picture_sort] => 1
    )

[1] => Array
    (
        [id] => 243
        [title] => Hotel
        [picture] => louis1.jpg
        [picture_sort] => 2
    )

[2] => Array
    (
        [id] => 243
        [title] => Hotel
        [picture] => louis3.jpg
        [picture_sort] => 3
    )

......等等

但我每个酒店只想要一个结果，所以我尝试了一个GROUP BY：

SELECT s25.entry_id AS id, 
s25.value AS title, 
s35.file AS picture, 
s86.value AS picture_sort 
FROM sym_entries_data_25 AS s25 
LEFT JOIN sym_entries_data_34 AS s34 ON (s25.entry_id = s34.relation_id)     
LEFT JOIN sym_entries_data_35 AS s35 ON (s34.entry_id = s35.entry_id) 
LEFT JOIN sym_entries_data_86 AS s86 ON (s34.entry_id = s86.entry_id) 
GROUP BY s25.value
ORDER BY s86.value

然后我只得到一个结果但是一个随机结果，而不是第一个结果：

[0] => Array
    (
        [id] => 243
        [title] => Hotel
        [picture] => louis3.jpg
        [picture_sort] => 3
    )

这可能是什么问题？

Answer 1

当您执行group by时，您无法保证您未分组的列的值。例如，如果您有一个包含列a和b的表，以及如下数据：

a | b
-----
1 | 2
1 | 3

如果您执行select * from table group by a，则可以获得2或3作为b的值。

如果您只想要酒店的最高结果，您需要做的不是分组，而是将picture_sort等于min(picture_sort)

的结果

MySQL GROUP BY杀死ORDER BY

1 个答案: