Updating display order of multiple MySQL rows in one or very few queries

Question

I have a table with say 20 rows each with a number for display order (1-20).

SELECT * FROM `mytable` ORDER BY `display_order` DESC;

From an adm

Answer 1

You could try to wrap it into a few statements, I don't think it's possible in a single one. So for example, let's say you are going to update the 10th row. You want every record after 10 to be bumped up.

UPDATE table SET col=col+1 WHERE col > 10
UPDATE table SET col=10 WHERE id = X
... 

But it's really tough to roll in all logic required. Because some records maybe need a decrement, etc.. You want to avoid duplicates, etc..

Think about this in terms of developer time vs. gain.

Because even if someone sorts this once per day, the overhead is minimal, compared to fixing it in a stored procedure, or pseudo-optimizing this feature so you don't run 20 queries. If this doesn't run 100 times a day, 20 queries are perfectly fine.