What do you mean by "creating code for each case"? 
SELECT 1 + COUNT(1)
INTO @sort
FROM t_tree AS t
WHERE t.f_parent_id = 2
LIMIT 1;

UPDATE t_tree AS t
SET f_sort = (@sort := @sort - 1)
WHERE T.f_parent_id = 2
ORDER BY f_sort DESC;

[download]

($q=q:Sq=~/;[c](.)(.)/;chr(-||-|5+lengthSq)`"S|oS2"`map{chr |+ord
}map{substrSq`S_+|`|}3E|-|`7**2-3:)=~y+S|`+$1,++print+eval$q,q,a,

[download]

In reply to Re: [OT] MySQL recalibrating a sort-index by choroba
in thread [OT] MySQL recalibrating a sort-index by LanX

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