MySQL: Split column by delimiter & replace numbers with values from another column

Question

Using MySQL, split column by delimiter & replace numbers with values from another column.

I have a column named 'path' having paths like '/426/427/428'. I would like to replace category numbers with category names. Result would be like '/Computers/Other accessories/Laser printers'.

This mysql query seems to be a good start, but don't know how to take column values from 'categories' table, 'path' column.

select distinct
  SUBSTRING_INDEX(SUBSTRING_INDEX((SELECT TRIM(LEADING '/' FROM '/426/427/428')), '/', numbers.n), '/', -1) name
from
  (select @rownum := @rownum + 1 as n
        from categories
        cross join (select @rownum := 0) r
    ) numbers 
where n > 0
order by
   n

Now this query splits the string correctly to:

426
427
428

Next would be to have a result like:

id    name
426   Computers
427   Other accessories
428   Laser printers

Finally should merge the 'name' column to

'/Computers/Other accessories/Laser printers'

string.

Thanks for your help in advance!

klor · Accepted Answer · 2018-04-20 13:19:27Z

I got the following query:

CREATE TEMPORARY TABLE IF NOT EXISTS 
t1
ENGINE=MyISAM
AS (
    SELECT
         n AS nr
         , SUBSTRING_INDEX(SUBSTRING_INDEX((SELECT TRIM(LEADING '/' FROM '/426/427/428')), '/', tmp.n), '/', -1) AS catid
         , (
                SELECT name FROM category
                WHERE category.id = catid
            ) AS name
         , (
                SELECT path FROM category
                WHERE category.id = catid
            ) AS path
    FROM
      (SELECT @rownum := @rownum + 1 AS n, category.id, category.name, category.path
            FROM category
            CROSS JOIN (SELECT @rownum := 0) r
        ) AS tmp 
    GROUP BY catid
    ORDER BY
       n

);

SELECT * FROM t1;
DROP TEMPORARY TABLE t1;

Result is:

*nr*   *catid*   *name*   *path*  
1   426   Computers   /426  
2   427   Other accessories   /426/427  
3   428   Laser printers   /426/427/428

This is almost good, just need to merge the name column with delimiters.

So final query is:

CREATE TEMPORARY TABLE IF NOT EXISTS 
t1
ENGINE=MyISAM
AS (
    SELECT
         n AS nr
         , SUBSTRING_INDEX(SUBSTRING_INDEX((SELECT TRIM(LEADING '/' FROM '/426/427/428')), '/', tmp.n), '/', -1) AS catid
         , (
                SELECT name FROM category
                WHERE category.id = catid
            ) AS name
         , (
                SELECT path FROM category
                WHERE category.id = catid
            ) AS path
    FROM
      (SELECT @rownum := @rownum + 1 AS n, category.id, category.name, category.path
            FROM category
            CROSS JOIN (SELECT @rownum := 0) r
        ) AS tmp 
    GROUP BY catid
    ORDER BY
       n

);

/* SELECT * FROM t1; */
SELECT group_concat(name SEPARATOR '/') as path_long FROM t1;
DROP TEMPORARY TABLE t1;

We get the following query result:

path_long
/Computers/Other accessories/Laser printers

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