CODEWITHSUNDEEP
mysqlsqlsql-order-byaggregate-functions
brain storm
brain storm

Reputation: 31252

why is mysql not returning correct order for varchar of floats?

I have a column version which is varchar but contains double values. when I try to get the latest (max) version I get incorrect results. But when I do min, I get correct result.

How is the ordering of varchar columns containing double determined?

Here is the content of my table;

    mysql> Desc Application;
    +---------+------------------+------+-----+---------+----------------+
    | Field   | Type             | Null | Key | Default | Extra          |
    +---------+------------------+------+-----+---------+----------------+
    | id      | int(11) unsigned | NO   | PRI | NULL    | auto_increment |
    | version | varchar(50)      | YES  |     | NULL    |                |
    +---------+------------------+------+-----+---------+----------------+
    2 rows in set (0.01 sec)

    mysql> select * from Application;
    +----+---------+
    | id | version |
    +----+---------+
    |  1 | 0.0.0   |
    |  2 | 0.0.1   |
    |  3 | 0.0.2   |
    |  4 | 0.1.0   |
    |  5 | 0.1.1   |
    |  6 | 0.1.2   |
    |  7 | 1.0.0   |
    |  8 | 1.0.1   |
    |  9 | 1.1.1   |
    | 10 | 8.7.3   |
    | 11 | 10.29.0 |
    +----+---------+
    11 rows in set (0.00 sec)

    select max(version) from application;
+--------------+
| max(version) |
+--------------+
| 8.7.3        |
+--------------+
1 row in set (0.00 sec)

mysql> select version from application
    -> ORDER BY version DESC
    -> LIMIT 1;
+---------+
| version |
+---------+
| 8.7.3   |
+---------+
1 row in set (0.00 sec)

mysql> select min(version) from application;
+--------------+
| min(version) |
+--------------+
| 0.0.0        |
+--------------+
1 row in set (0.00 sec)

Upvotes: 0

Views: 160

Answers (1)

user1864610
user1864610

Reputation:

Forget the idea that these are floats. MySQl sees them as character strings because that's what you've told it.

Sorting by character order, 8 is the largest, and 0 is the minimum, so your results are correct.

If you want MySQL to sort by numerical order, give it numerical fields. Alternatively, right-align and zero-pad your subfields - 08.07.03 is less than 10.29.00

Upvotes: 4

Related Questions