Mysql query trivia - mysql

Question

Updated: Please assume, I will have exactly 4 elements in my version number x.x.x.x
Table xyz (id int, os varchar, version varchar)
id os version
1 mac 1.0.0.4
2 android 1.0.1.2
3 mac 1.0.0.14
4 mac 1.0.0.07
I want to find the maximum version number of each operating system.
select max(version), os from xyz group by os
but in the above data sample, it returns 1.0.0.4 as the highest version of mac, rather than returning 1.0.0.14. Is there any way to fix the above query? I know version is varchar :( If there is NO solution possible, then I can change datatype to other, but that will still not solve the issue.

Answer 1

If the 4 parts in the version are all numbers and not bigger than 255, you can use the INET_ATON() function, and its reverse INET_NTOA():
SELECT INET_NTOA(MAX(INET_ATON(version))), os
FROM xyz
GROUP BY os ;
Tested in SQL-Fiddle

Answer 2

Mysql uses text sort for this field when you try to get max:
SELECT version FROM test ORDER BY VERSION;
1.0.0.14
1.0.0.4
1.0.07
1.0.1.2.4
But even if you try to cast this to integer, you will get
SELECT version FROM test ORDER BY CAST(VERSION AS SIGNED);
1
1
1
1
And this really has a sense. How do you want MySQL to guess, what you want?
MySQL should be used to store data, and you should format it yourself.
A fine solution would be to use several fields for version:
id int, os varchar, versionMajor int, versionMinor int, versionMoreMinor int, versionEvenMoreMinor int
You should be able to sort and to format them as you wish.

Answer 3

It is ugly, but it's doing the job:
select t1.os,t1.version from xyz t1 where (t1.os,
((cast(SUBSTRING_INDEX(t1.version, '.', 1) as unsigned)+1)*1000
+(cast(SUBSTRING_INDEX(SUBSTRING_INDEX(t1.version, '.', -3), '.', 1) as unsigned)+1)*100
+(cast(SUBSTRING_INDEX(SUBSTRING_INDEX(t1.version, '.', -2), '.', 1) as unsigned)+1)*10
+(cast(SUBSTRING_INDEX(t1.version, '.', -1) as unsigned))+1))
=(select t2.os,
max((cast(SUBSTRING_INDEX(t2.version, '.', 1) as unsigned)+1)*1000
+(cast(SUBSTRING_INDEX(SUBSTRING_INDEX(t2.version, '.', -3), '.', 1) as unsigned)+1)*100
+(cast(SUBSTRING_INDEX(SUBSTRING_INDEX(t2.version, '.', -2), '.', 1) as unsigned)+1)*10
+(cast(SUBSTRING_INDEX(t2.version, '.', -1) as unsigned))+1)
from xyz t2 where t2.os=t1.os);
sqlfiddle

Answer 4

What you'd really like to do here is use a SPLIT function, but that's not available in MySQL. However, you can write a user-defined function that will do the same thing, or refactoring this function code into a view.
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, '');
Source.
Additionally, you may want to consider that the reason this is such a pain in the butt is because you're essentially violating first normal form. A version number of the form you specify is actually four distinct values: major version, minor version, revision (or maintenance), and build. Your table structure should use the same format:
Table xyz (id int not null, os varchar not null, version_major int not null, version_minor int not null, version_revision int null, version_build int null)
Then you just use an ORDER BY clause to sort the data. You can use a calculated field or a view to display the formatted version number.
Now, I know why you chose to use a single field. Version numbers are inconsistent, and many version numbers do not include revision or build values, other include letters, etc. You can change the int to a varchar and cover 90% of cases in my experience, however.

Answer 5

You may try to convert string to the integer and get MAX()
SELECT MAX( CONVERT( REPLACE( `version`, '.', '' ), UNSIGNED ) ) from xyz
upd
There are some another way with ending detection, but it doesn't work properly with minor version, maybe you will tune this heavy query to get it works well for you
SELECT `version`,
CONVERT(
CONCAT_WS( '.',
REPLACE( SUBSTRING( `version`, 1, ( CHAR_LENGTH( `version` ) - LOCATE( '.', REVERSE( `version` ) ) ) ), '.', '' ),
SUBSTRING( `version`, 1 + LOCATE( '.', REVERSE( `version` ) ) * -1 )
),
DECIMAL ( 10, 3 )
)
FROM `xyz`
sorry, code improved

Answer 6

Thanks to #ntvf for idea.
This will do what I am looking for.
select a.os, xyz.version from xyz,
(SELECT os, MAX( CONVERT(REPLACE(`version`,'.',''),UNSIGNED)) as version from xyz group by os) a
where
a.os=xyz.os and
CONVERT(REPLACE( xyz.version, '.', '' ), UNSIGNED) = a.version