如何从字符串中获取临时表结果？

Question

for example:
my products best sort string is "'8207,17631,16717,18545,9062,17469,17246,17750"

this string is posted from php , I dont want to store them in datebase. I want to query datas from mysql and left join a temp table then sort by the temp table'sort.

how can I get this temp table from a string ?

my codes seems will be like that bellow:(wrong codes)

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

Your best approach could be - to use UNION for generating row set from string. This, however, will require joining your string in your application, like this:

$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)));

-end result will be like:

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

However, if you want to do that in SQL - that will not be easy, since MySQL doesn't supports sequences - and, therefore, you'll need to use some tricks to produce desired rows set. There's a way to generate N consecutive numbers with:

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

-this will result in 10 numbers 1..10 (check this fiddle). Using this, you can get your end result:

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

-check this fiddle. However, this may be slow and I recommend you to use your application layer to build desired SQL.

Answer 2

something like this? use UNION to generate inline view. this can be generated by Client side.

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