Question

I have a table data with following columns:

|-a-|-b-|-text-|

|-1-|-1-|-text-|

|-1-|-2-|-text-|

|-1-|-3-|-text-|

|-2-|-1-|-text-|

|-2-|-2-|-text-|

|-2-|-3-|-text-|

|-2-|-4-|-text-|

e.g. I am on 3rd record ($current – in bold), I need to make sql query to move to (2, 1).

I have the query as below:

$previous = "SELECT a, b FROM `table` WHERE a <= $current_a AND b < $current_b ORDER BY a DESC, b DESC LIMIT 1";
$next = "SELECT a, b FROM `table` WHERE a >= $current_a AND b > $current_b ORDER BY a ASC, b ASC LIMIT 1";

Though however next goes to (2, 4) instead.

Any ideas?

Answer 1

You need a condition that handles the two cases separately; when the a values are the same, and when they are different:

where (a = @current_a and b > @current_b) or (a > @current_a)

You need that for the previous item also:

where (a = @current_a and b < @current_b) ro (a < @current_a)