db field(GROUP_CONCAT) as array

问题

MY tables..

articles fields:

• id
• name

cats fields:

• id
• name

article_cats fields:

• id
• article_id
• cat_id

I have this sql:

SELECT
  a.id AS article_id ,
  a.name AS article_name ,
  COUNT( c.id ) AS num_categories ,
  GROUP_CONCAT( c.name ) AS categorie_names
 FROM
  articles AS a
 LEFT JOIN
  article_cats AS ac
 ON
  ( a.id = ac.article_id )
 LEFT JOIN
  cats AS c
 ON
  ( ac.cat_id = c.id )
 GROUP BY
  a.id 

and it provide this table structure:

what i need is, to get categories id and name in array, so categorie_names will be an array with fields cat_id and cat_name for each category.

Is this possible with mysql ?

回答1:

In database array means tables. If you want data in array format the best way to store the values in a seperate temporary table.

Like

article_id, category_id, category_name
1           1            Cat1
2           1            Cat1
3           2            Cat2
3           1            Cat1

Or you have to use a concatenation inside the group_concat

GROUP_CONCAT(cast(concat(c.id,\': \',c.name) AS char)SEPARATOR \', \') AS categorie_names

So the result will be like 2:Cat2,1:Cat2. You can split(first with ',' then ':') this value and retrieve ID and Name.

来源：https://stackoverflow.com/questions/12126047/db-fieldgroup-concat-as-array