Question

I have a database that all have a unique ID. They are in ascending order, and I would like to do..

update text SET name = 'hello french man' where id=1;

And change the name of every row to this data I have. So I can keep incrementing

id = id + 1;

But the problem occurs here, I’ve deleted some rows in the past, so there are missing IDs. For instance, there’s row 1,2,3,5. Row 4 is missing because I had deleted it, so how can I update every row without skipping a name because updating row 4 won’t do anything?

It is crucial that I have a 1-1 mapping with all of them and do not skip any names since order matters.

Thanks, any help is much appreciated!

Answer 1

You can use this solution:

UPDATE tbl a
INNER JOIN
(
    SELECT id, @rn:=@rn+1 AS rn
    FROM tbl
    CROSS JOIN (SELECT @rn:=0) var_init
    ORDER BY id
) b ON a.id = b.id
LEFT JOIN
(
    SELECT id, @rn2:=@rn2+1 AS rn
    FROM tbl
    CROSS JOIN (SELECT @rn2:=-1) var_init
    ORDER BY id
) c ON b.rn = c.rn
SET a.id = COALESCE(c.id, a.id + 1)

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See the SQLFiddle Demo