Sorting/ordering in MySQL

Question

I\'m having a little problem with trying to sort the contents of a table programs by the column prog_id which holds the id of each program in the f

Answer 1

You could split them into their constituent parts like:

SELECT REPLACE(SUBSTRING(SUBSTRING_INDEX(prog_id, '.', 1),
       LENGTH(SUBSTRING_INDEX(prog_id, '.', 1 -1)) + 1),
       '.', '') AS id1,
       REPLACE(SUBSTRING(SUBSTRING_INDEX(prog_id, '.', 2),
       LENGTH(SUBSTRING_INDEX(prog_id, '.', 2 -1)) + 1),
       '.', '') AS id2,
       REPLACE(SUBSTRING(SUBSTRING_INDEX(prog_id, '.', 3),
       LENGTH(SUBSTRING_INDEX(prog_id, '.', 3 -1)) + 1),
       '.', '') AS id3
FROM programs
ORDER BY CAST(id1 AS INT(4)), CAST(id2 AS INT(4)), CAST(id3 AS INT(4))

The best method would be to create the the extra fields like yoda2k says, but if you don't have that access then you could use the above.

You could encapsulate that into a function like:

CREATE FUNCTION SPLIT_STR(
  x VARCHAR(255),
  delim VARCHAR(12),
  pos INT
)
RETURNS VARCHAR(255)
RETURN REPLACE(SUBSTRING(SUBSTRING_INDEX(x, delim, pos),
       LENGTH(SUBSTRING_INDEX(x, delim, pos -1)) + 1),
       delim, '');

Then do:

SELECT SPLIT_STR(prog_id, '.', 1) AS id1,
   SPLIT_STR(prog_id, '.', 2) AS id2,
   SPLIT_STR(prog_id, '.', 3) AS id3,
FROM programs
ORDER BY CAST(id1 AS INT(4)), CAST(id2 AS INT(4)), CAST(id3 AS INT(4))