Mysql: Swap data for different rows

Question

Suppose a table fruits that looks like this:

------------------------------------------
| id |    name    |   color   | calories |
-------------         


        

Answer 1

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 2

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 3

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.

Answer 4

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.