MySQL query to reorder field values? - mysql

Question

I have table like this:
===============
| rank | name |
===============
| 3 | john |
| 6 | bob |
| 10 | alex |
| 11 | brad |
| 12 | matt |
| 34 | luke |
| 145 | ben |
===============
(this table is an example. In reality my table consists of ~5000 rows of data).
Is there a query to reorder the rank values starting from 1 and going up so it ends up like this:
===============
| rank | name |
===============
| 1 | john |
| 2 | bob |
| 3 | alex |
| 4 | brad |
| 5 | matt |
| 6 | luke |
| 7 | ben |
===============
It would be preferable to do this in 1 or 2 queries, not 1 query for each row since my table has 5000+ rows.
EDIT: Sorry I wasn't clear. I am trying to UPDATE the values in the database.

Answer 1

This is a little crude but will work in a pinch.
First order your table correctly just incase
ALTER TABLE tablename ORDER BY rank
Then drop the column
ALTER TABLE tablename DROP rank
Then add it again, with auto increment
ALTER TABLE tablename ADD COLUMN rank INT NOT NULL AUTO_INCREMENT FIRST
The auto increment will take care of numbering them in order, plus you don't have to loop through each row.

Answer 2

Here is the solution I came up with for this problem:
1.Create a temporary table without any keys
CREATE TEMPORARY TABLE tempTable (
id INT(11) NOT NULL
)
COLLATE='latin1_swedish_ci'
ENGINE=MyISAM
ROW_FORMAT=DEFAULT;
2.Populate the temporary table with data from the original table, ordered by rank
INSERT INTO tempTable SELECT id FROM myTable ORDER BY rank;
3.Add auto-incrementing rank column, giving all rows a unique rank, counting up from 1
ALTER TABLE tempTable
ADD COLUMN `rank` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
ADD PRIMARY KEY (`rank`);
4.Update the original table with a join to the temp table, overriding the original ranks
UPDATE myTable
INNER JOIN tempTable
ON myTable.id = tempTable.id
SET myTable.rank = tempTable.rank;
5.Drop the temp table
DROP TABLE tempTable;

Answer 3

An alternative to a strict MySQL solution would be to loop through the rows with a scripting language. Not a great idea if you have a large table, but could be acceptable if this is a one time fix.
In PHP
$db = mysql_connect('localhost', 'user', 'password');
mysql_select_db('database', $db);
$result = mysql_query("SELECT rank
FROM myTable
ORDER BY rank");
$i = 1;
while ($row = mysql_fetch_assoc($result)) {
mysql_query("UPDATE myTable
SET rank = " . $i++ . "
WHERE rank = " . $row['rank']);
}
Note that this will only work if rank is unique and you traverse in an order.

Answer 4

set #a:=(select max(id) from mytable)+1;
update mytable set id=(#a:=#a+1)
order by id;
set #a := 0;
update mytable set id=(#a:=#a+1)
order by id;
simple way, work for me. easy way.