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Editorial Team
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Asked: 2026-06-06T22:05:18+00:00

I’m writing a video game in javascript on a server that saves info in

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I’m writing a video game in javascript on a server that saves info in a mysql database and I am trying to make my first effect attached to simple healing potion item. To implement the effect I call a spells table using spell_id and it gets a field called effect containing the code to execute on my server. I use the eval() function to execute the code in the string. In order to optimize the game I want to run as few queries as possible. For this instance (and I think the answer will help me evaluate other similar effects) I want to update the ‘player’ table which contains a stat column like ‘health’ then I want it to add n which will be a decreasing number 15 then 250 ms later add 14 then 13 until that n=1 the net effect is a large jump in health then smaller and smaller accomplishing this is relatively easy if the player’s health reaches his maximum allowed limit the effect will stop immediately…
but I’d like to do a single update statement for each increase rather than a select and an update every 250ms to check if health > max_health and make sure the player’s health doesn’t go above his max health. So to digress a bit I’d like a single update that given this data

player_id   health   max_health
=========   ======   ==========
1           90       100

will add 15 to health unless (max_health-health) < 15… in this case it should only add 10.

An easier solution might be
if I could just return health and max health after each update I update it I don’t mind doing a final
pseudo code
if health > max_health
update health set health = max health

So if anyone could explain how to return fields after an update that would help.
Or if anyone could show how to use logic within the update that would also help.

Also, If I didn’t give enough information I’m sorry I’d be glad to provide more I just didn’t want to make the question hard to understand.

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1 Answer

  1. Editorial Team
    update health
set health = least(max_health, health +<potion effect>)
where player_id = ...

    EDIT

    For your other question : normally, i think that update returns the number of affected rows. So if you try to update health when health is already = max_health, it should return 0.

    I’d know how to do this in php, for example, but just said you where using javascript… so ?

    http://dev.mysql.com/doc/refman/5.6/en/update.html

    UPDATE returns the number of rows that were actually changed. The
    mysql_info() C API function returns the number of rows that were
    matched and updated and the number of warnings that occurred during
    the UPDATE.

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