Php MySQL在一个查询中多次选择检索嵌套数组

[更新]

我尝试从一个表中选择数据，但尝试以不同的顺序获取它们

SELECT * FROM 
(
  SELECT * FROM videos ORDER BY timestamp DESC
) mostrecent

UNION ALL

SELECT * FROM
( 
  SELECT * FROM videos ORDER BY timestamp ASC
) oldest

现在，这将以不同的顺序检索记录。最新的视频和最旧的视频

foreach($table as $key=>$value)
{
$row_tmb[$key] = $value;
}
$array[] = $row_tmb;

---

打印数据时

print_r($array);

我明白了

Array ( [0] => Array ( [vid] => 1 [title] => title1 [timestamp] => newer) 
        [1] => Array ( [vid] => 2 [title] => title2 [timestamp] => older
        //from second select...
        [2] => Array ( [vid] => 2 [title] => title2 [timestamp] => older
        [3] => Array ( [vid] => 1 [title] => title1 [timestamp] => newer
)

我想要

Array('newest' => Array ( 
        [0] => Array ( [vid] => 1 [title] => title1 [timestamp] => newer) 
        [1] => Array ( [vid] => 2 [title] => title2 [timestamp] => older))
        //from second select...
Array('oldest' => Array (
        [0] => Array ( [vid] => 2 [title] => title2 [timestamp] => older
        [1] => Array ( [vid] => 1 [title] => title1 [timestamp] => newer))

---

可以在select语句中使用如下外部查询：

select
    *
from
    (
        SELECT
            'Newest',col1,col2,etc
        FROM
            (
            SELECT 
                * 
            FROM 
                videos 
            ORDER BY 
                timestamp DESC
            )mostrecent
        UNION ALL
        SELECT
            'Oldest',col1,col2,etc
        FROM
            (
            SELECT 
                * 
            FROM 
                videos 
            ORDER BY 
                timestamp DESC
            )oldest
    ) someTable
order by
    1 asc

(
    SELECT *, 'newest' AS source, timestamp AS sortColumn
    FROM videos
)
UNION ALL
(
    SELECT *, 'oldest' AS source, -timestamp AS sortColumn
    FROM videos
)
ORDER BY sortColumn DESC

(
    SELECT *, 'newest' AS source, timestamp AS sortColumn
    FROM videos
    ORDER BY timestamp DESC
    LIMIT 100
)
UNION ALL
(
    SELECT *, 'oldest' AS source, nbVotes AS sortColumn
    FROM videos
    ORDER BY timestamp ASC
    LIMIT 100
)
ORDER BY sortColumn DESC

然后，这将首先按最新/最旧的结果排序，然后按您拥有的结果排序

这不会像显示所需的输出那样为您提供两个数组，但它将为您提供与您所需相同的内容，除了在一个数组中。不过，您可以简单地检查PHP代码中的第一列，然后将其放入正确的数组中，以获得所需的嵌套数组

---

编辑：将别名添加到派生表中。不要吹毛求疵，但在你写“甚至都不起作用”的同时，你本可以找出遗漏并进行有效的查询。来吧，伙计，这里的答案是为了帮助你，而不是为了帮你完成工作：）

我知道这是一个理想的答案，但至少我不必再查询两次。 因为我知道每次选择只需要两条记录

$newest = array($videos[0], $videos[1]);
$oldest = array($videos[2], $videos[3]);

现在，当检索到html时，这甚至更容易处理…

清楚地指出：对单个SELECT语句使用ORDER BY并不意味着行在最终结果中的显示顺序，因为默认情况下，UNION会生成一组无序的行

我建议您使用一个简单的查询：

SELECT *
FROM videos
ORDER BY timestamp DESC

在PHP数组中获取数据，然后使用PHP代码复制它，并根据需要组合它。这是一些使用

mysqli

的示例代码。使用

PDO

与此类似：

// You should add a LIMIT to the query or it will take a lot of time and consume
// a lot of memory when the table gets bigger (several thousand rows)
$query  = 'SELECT * FROM videos ORDER BY timestamp DESC';
$result = mysqli_query($connection, $query);

// Retrieve the data
$data = array();
while ($row = mysqli_fetch_assoc($result)) {
    $data[] = $row;
}

// Use the retrieved data to get the combined result
$array = array(
    'newest' => $data,
    'oldest' => array_reverse($data),
);

更新：

假设列

timestamp

包含一个整数值（时间戳），您可以通过以下查询从

MySQL

获得相同的结果：

select
    *
from
    (
        SELECT
            'Newest',col1,col2,etc
        FROM
            (
            SELECT 
                * 
            FROM 
                videos 
            ORDER BY 
                timestamp DESC
            )mostrecent
        UNION ALL
        SELECT
            'Oldest',col1,col2,etc
        FROM
            (
            SELECT 
                * 
            FROM 
                videos 
            ORDER BY 
                timestamp DESC
            )oldest
    ) someTable
order by
    1 asc

(
    SELECT *, 'newest' AS source, timestamp AS sortColumn
    FROM videos
)
UNION ALL
(
    SELECT *, 'oldest' AS source, -timestamp AS sortColumn
    FROM videos
)
ORDER BY sortColumn DESC

(
    SELECT *, 'newest' AS source, timestamp AS sortColumn
    FROM videos
    ORDER BY timestamp DESC
    LIMIT 100
)
UNION ALL
(
    SELECT *, 'oldest' AS source, nbVotes AS sortColumn
    FROM videos
    ORDER BY timestamp ASC
    LIMIT 100
)
ORDER BY sortColumn DESC

如果

时间戳

列不是整数值，而是

日期

，则使用

FROM_UNIXTIME（时间戳）作为排序列

。其思想是计算一个可用于最终排序的值（在

UNION

级别），并将其存储在新列

sortColumn

中

PHP中使用

source

列来了解每条记录所属的组（最新记录与最旧记录）

备注：对于中型和大型表（数千行或更多行），它将运行缓慢，因为它无法使用索引。对于这种大小的表，无论如何选择所有记录都没有多大意义。您可能会这样写：

select
    *
from
    (
        SELECT
            'Newest',col1,col2,etc
        FROM
            (
            SELECT 
                * 
            FROM 
                videos 
            ORDER BY 
                timestamp DESC
            )mostrecent
        UNION ALL
        SELECT
            'Oldest',col1,col2,etc
        FROM
            (
            SELECT 
                * 
            FROM 
                videos 
            ORDER BY 
                timestamp DESC
            )oldest
    ) someTable
order by
    1 asc

(
    SELECT *, 'newest' AS source, timestamp AS sortColumn
    FROM videos
)
UNION ALL
(
    SELECT *, 'oldest' AS source, -timestamp AS sortColumn
    FROM videos
)
ORDER BY sortColumn DESC

(
    SELECT *, 'newest' AS source, timestamp AS sortColumn
    FROM videos
    ORDER BY timestamp DESC
    LIMIT 100
)
UNION ALL
(
    SELECT *, 'oldest' AS source, nbVotes AS sortColumn
    FROM videos
    ORDER BY timestamp ASC
    LIMIT 100
)
ORDER BY sortColumn DESC

---

选择最近的100行和最旧的100行。最后的结果从按

时间戳排序的最新记录开始（首先是最新的），然后是按他们收到的投票数排序的最旧记录（列
nbvoces
），递减（我假设没有视频的投票数超过13亿）.
您的问题不清楚。请解释清楚。我希望这将有助于澄清您是否没有限制条款？我可能需要限制每个selecttoo@MustafaMJalal：是的。给定的查询没有问题，它说每个派生表都必须有自己的表alias@MustafaMJalal：看来已经修好了。@MustafaMJalal:那你到底需要什么？如果你不解释你的实际问题，我们怎么可能回答你的问题呢，
UNION
不保留由它组合的
SELECT
s生成的行的顺序，也不保证第一个
SELECT
生成的行在第二个
SELECT
生成的行之前。当与
限制
组合使用时，在
选择
查询上使用
按
排序很有用。为了实现对
UNION
ed结果集的排序，您必须将
SELECT
s括在括号中，并在
UNION
级别添加
order BY
子句a。为了保持行的顺序，您可以选择一个额外的计算列，其中包含一个正确构建的表达式。我用一个只使用
SQL
的解决方案更新了答案。