SQL Order By but invert for one element - mysql

Question

I've got an SQL query which results upto the following
Code int1 int2 int3 S
C12 21 22 14 1
C33 43 56 2 3
C34 23 2 1 3
C55 33 92 12 5
CB56 45 66 10 5
MA10 10 11 12 1
This is the result of using OrderBy on Code
However I do not want it to order according to alphabets
But by the number after it for ex 1 in M1 and 33 in C33
In some cases the number after the alphabet may be 3 digits like E344
What I want it to look like
Code int1 int2 int3 S
MA10 10 11 12 1
C12 21 22 14 1
C323 43 56 2 3
C325 43 56 2 3
C34 23 2 1 3
C525 33 92 12 5
CB56 45 66 10 5
What I need is
M Should always show on top if Present
Then Sort According to Number on first place
Then Sort it according to the number on the Second place
Then sort it according to the number on the third place
The field 's' will always consist of the first digit from the Code

Answer 1

step 1 split up the column into 2 columns, 1 containing the letters, the other containing the numbers:
SELECT
substring(code,0,PATINDEX('%[0-9]%', Code)) as letters,
substring(code,PATINDEX('%[0-9]%', Code)) as numbers,
fields
FROM table
step 2 Convert the numbers to integer and sort
CONVERT(substring(code,PATINDEX('%[0-9]%', Code)),UNSIGNED INTEGER) as numbers
step 3 sort
Order by field1 asc, field2 desc... etc
It might be easier to use a subquery:
select * from
(SELECT
substring(code,0,PATINDEX('%[0-9]%', Code)) as letters,
CONVERT(substring(code,PATINDEX('%[0-9]%', Code)),UNSIGNED INTEGER) as numbers,
fields
FROM table) T
order by numbers asc, letters desc

Answer 2

This is conceptually simple: you want to order first by whether the code starts or not with the letter 'M', and then by the numeric portion of the code. You say in a comment:
extracting the first digit then order and then extracting the second
digit and then order and then extracting the third digit and then
order
This is exactly how alphabetical order has always worked. You order by first character; when it is the same you order by the second character, etc. so you need no special treatment for that case. Just get the numeric part of the code as a string, then order by it.
At this point, the only problem left to resolve is how to extract the numeric part of the code. That would be easy with PATINDEX() (as Alfons pointed out) but unfortunately MySQL does not support PATINDEX() as far as I know.
Now, what follows is extremely ugly, but it does work. Basically we get the non-numeric part of the string by removing all the numeric characters from it, then use the length of the non-numeric part to extract the numeric part.
SELECT mytable.* FROM mytable
INNER JOIN (
SELECT
code,
RIGHT(code, LENGTH(letters)) numbers
FROM (
SELECT
code,
REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
REPLACE(REPLACE(REPLACE(REPLACE(REPLACE(
code, 0, ''), 1, ''), 2, ''), 3, ''), 4, '')
, 5, ''), 6, ''), 7, ''), 8, ''), 9, '') letters
FROM mytable
) letters_table
) numbers_table
ON numbers_table.code = mytable.code
ORDER BY (numbers_table.code like 'M%') DESC,
numbers_table.numbers ASC
This solution is probably inefficient. However, I don't think you can get any acceptable efficiency anyway unless you store the numeric part on a separate column that you can index.

Answer 3

As you are guaranteeing that s is the value of the first digit in the code, this can be used to find the start of the code and from there, get the numeric part of the code. As you want to have all the codes starting with 'M' first, this results in the following ORDER BY clause:
... ORDER BY IF(SUBSTR(code, 1, 1) = 'M', 0, 1), SUBSTR(code, LOCATE(s, code))