如何從字符串中獲取臨時表結果？

Question

例如：
我的產品最好排序字符串是''8207,17631,16717,18545,9062,17469,17246,17750“

這個字符串是從php發布的，我不想將它們存儲在datebase中。 我想從mysql查詢數據並離開加入臨時表然后按臨時表的排序。

如何從字符串中獲取此臨時表？

我的代碼似乎就像下面那樣:(錯誤的代碼）

select
    p.products_id
from
    (
        select '18207,17631,16717,18545,9062,17469,17246,17750' as products_id
    ) as p
order by p.sort

Answer 1

您最好的方法可能是 - 使用UNION從字符串生成行集。 但是，這需要在您的應用程序中加入您的字符串，如下所示：

$string = '18207,17631,16717,18545,9062,17469,17246,17750';
$id     = 0;
$sql    = join(' UNION ALL '.PHP_EOL, array_map(function($item) use (&$id)
{
   return 'SELECT '.(++$id).' AS sort, "'.$item.'" AS products_id';
}, explode(',', $string)));

- 結果將如下：

SELECT 1 AS sort, "18207" AS products_id UNION ALL 
SELECT 2 AS sort, "17631" AS products_id UNION ALL 
SELECT 3 AS sort, "16717" AS products_id UNION ALL 
SELECT 4 AS sort, "18545" AS products_id UNION ALL 
SELECT 5 AS sort, "9062" AS products_id UNION ALL 
SELECT 6 AS sort, "17469" AS products_id UNION ALL 
SELECT 7 AS sort, "17246" AS products_id UNION ALL 
SELECT 8 AS sort, "17750" AS products_id

但是，如果你想在SQL中這樣做 - 這並不容易，因為MySQL不支持序列 - 因此，你需要使用一些技巧來產生所需的行集。 有一種方法可以生成N個連續數字：

SELECT id+1
FROM 
  (SELECT
    (two_1.id + two_2.id + two_4.id + 
    two_8.id + two_16.id) AS id
   FROM
    (SELECT 0 AS id UNION ALL SELECT 1 AS id) AS two_1
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 2 id) AS two_2
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 4 id) AS two_4
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 8 id) AS two_8
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 16 id) AS two_16
   ) AS init
LIMIT 10

- 這將導致10數字1..10 （檢查這個小提琴）。 使用此功能，您可以獲得最終結果：

SELECT 
  ELT(id+1, 18207,17631,16717,18545,9062,17469,17246,17750) AS products_id,
  id+1 AS sort
FROM 
  (SELECT
    (two_1.id + two_2.id + two_4.id + 
    two_8.id + two_16.id) AS id
   FROM
    (SELECT 0 AS id UNION ALL SELECT 1 AS id) AS two_1
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 2 id) AS two_2
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 4 id) AS two_4
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 8 id) AS two_8
    CROSS JOIN (SELECT 0 id UNION ALL SELECT 16 id) AS two_16
   ) AS init
HAVING 
  products_id IS NOT NULL

- 檢查這個小提琴。 但是，這可能很慢，我建議您使用應用程序層來構建所需的SQL。

Answer 2

這樣的事情？ 使用UNION生成內聯視圖。 這可以由客戶端生成。

SELECT *
FROM
(
    SELECT '18207' AS products_id, 1 as sort
    UNION
    SELECT '17631' AS products_id, 2 as sort
    UNION
    SELECT '16717' AS products_id, 3 as sort
    UNION
    SELECT '18545' AS products_id, 4 as sort
    UNION
    SELECT '9062' AS products_id, 5 as sort
) x JOIN tbl x.products_id = tbl.products_id
ORDER BY sort