Mysql: Swap data for different rows - mysql

Question

Suppose a table fruits that looks like this:
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| id | name | color | calories |
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| 1 | apple | red | 20 |
| 2 | orange | orange | 10 |
| 3 | grapes | green | 5 |
| 4 | bananas | yellow | 15 |
| 5 | plum | purple | 25 |
------------------------------------------
How can I swap the values of a row, with another, leaving the id number intact?
Example:
SWAP ROW WITH ID "5" WITH ROW WITH ID "2"
Result:
------------------------------------------
| id | name | color | calories |
------------------------------------------
| 1 | apple | red | 20 |
| 2 | plum | purple | 25 |
| 3 | grapes | green | 5 |
| 4 | bananas | yellow | 15 |
| 5 | orange | orange | 10 |
------------------------------------------
Note that all the values are intact except for the id.
I need to do this with a really large list of values, so I need a one-liner, or at most, something that doesn't require the creation of temporary tables, and things like that.
Note: id is unique
Thank you

Answer 1

You could use a join inequality to line up the rows you want to swap:
update fruit a
inner join fruit b on a.id <> b.id
set a.color = b.color,
a.name = b.name,
a.calories = b.calories
where a.id in (2,5) and b.id in (2,5)
http://sqlfiddle.com/#!18/27318a/5

Answer 2

Since ID is unique, it is difficult to just swap the IDs, it's easier to swap the column contents. A query like this might be what you need:
UPDATE
yourtable t1 INNER JOIN yourtable t2
ON (t1.id, t2.id) IN ((1,5),(5,1))
SET
t1.color = t2.color,
t1.name = t2.name,
t1.calories = t2.calories
Please see fiddle here.

Answer 3

Here's a way to store values temporarily without using a temp table or a dummy row in your fruit table:
SELECT name, color, calories FROM fruit WHERE id = 2 INTO #name, #color, #calories;
UPDATE fruit AS f1, fruit AS f2
SET
f1.name = f2.name, f2.name = #name,
f1.color = f2.color, f2.color = #color,
f1.calories = f2.calories, f2.calories = #calories
WHERE (f1.id, f2.id) = (2, 5);
Here's another solution that uses a dummy id value:
UPDATE fruit SET id = 0 WHERE id = 5;
UPDATE fruit SET id = 5 WHERE id = 2;
UPDATE fruit SET id = 2 WHERE id = 0;

Answer 4

If your operations are based on ID, and you want to swap entire rows, a fancy way of swapping UNIQUE IDs is to start numbering them at 1, and use 0 as a temporary value.
Another way of performing this is using an unsigned column, and using a designated value (ie.: -1) for temporary. I wouldn't really recommend the latter, as we are effectively wasting space with this method. See http://dev.mysql.com/doc/refman/5.0/en/numeric-type-overview.html for more details.