在CakePHP查询中获取不同的不同DISTINCT结果

Question

我接受了答案。但欢迎提出更多答案和建议。

我变得与众不同 - 在CakePHP查询中使用distinct时，MySQL结果不同。

我要做的是： date_generated 字段的不同结果。

问题：查询1工作正常，但是当我收到两个字段（date_generated，id）（请参阅查询2）时，不同结果无效。

查询1

$this->Purchase->find('all',array( 
                               'order' => array('Purchase.date_generated ASC'),
                               'fields' => array('DISTINCT Purchase.date_generated')));

查询1的结果：在此结果中 date_generated 不重复且工作正常。请查看查询2.

Array
(
    [0] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 1970-01-01
                )

        )

    [1] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-17
                )

        )

    [2] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-18
                )

        )

    [3] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-19
                )

        )

    [4] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-22
                )

        )

    [5] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-29
                )

        )

    [6] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-08-01
                )

        )

)

查询2 ：仅添加了＆＃39; Purchase.id＆＃39;

$this->Purchase->find('all',array( 
                               'order' => array('Purchase.date_generated ASC'),
                               'fields' => array('DISTINCT Purchase.date_generated','Purchase.id')));

查询2的结果：在此结果数组索引5,6,7 date_generated重复。

Array
(
    [0] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 1970-01-01
                    [id] => 9
                )

        )

    [1] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-17
                    [id] => 1
                )

        )

    [2] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-18
                    [id] => 2
                )

        )

    [3] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-19
                    [id] => 3
                )

        )

    [4] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-22
                    [id] => 4
                )

        )

    [5] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-29
                    [id] => 5
                )

        )

    [6] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-29
                    [id] => 6
                )

        )

    [7] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-06-29
                    [id] => 7
                )

        )

    [8] => Array
        (
            [Purchase] => Array
                (
                    [date_generated] => 2014-08-01
                    [id] => 8
                )

        )

)

Answer 1

这似乎是标准的sql行为。第一个查询产生类似这样的东西

选择 DISTINCT Purchase.date_generated 从 采购 订购 Purchase.date_generated ASC

第二个产生类似

的查询

选择 DISTINCT Purchase.date_generated， Purchase.id 从 采购 订购 Purchase.date_generated ASC

这些查询的结果正是您所获得的。对于socond，它将返回不同的Purchase.date_generated和Purchase.id对。因此，如果某个日期有几个购买ID，则每个购买ID都是不同的对。

因此，如果您仅在明确日期之后，则应使用第一个查询。