if(SQL SELECT) { do something; } ????

Question

I need to do an action based on a mySQL SELECT result... for example if result = 1 do something and change register to 0. If result = 0, do another thing and change register to 1. The thing is that multiple people will using the game, so, how can I be sure that, between the time I did the sql query and the time I do the action and change the value, someone else hasn't modified the value already?

EDIT: Javascript language ;) EDIT 2: This is solved only with transactions? the first query is a select and the second one is an update.

Answer 1

Answer by softrare · Mar 26, 2012 at 02:02 PM

I hope you program in C# ^^

 private UnityEngine.Object queueLock = new UnityEngine.Object();
 
 public void ...(..)  {
   if (something) {
     lock (queueLock){
       //critical action (like setting a global variable)
     }
   }
 }

this should put you on the right track :)

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Answer 2

Answer by jakovd · Mar 26, 2012 at 02:11 PM

This is actually not a Unity question, but here is a suggestion for solving your problem anyway. This is a common problem which is solved by using transactions. Google "mysql transaction". Your problem is similar to a problem of withdrawing money from account, which is often used in transaction examples.

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if(SQL SELECT) { do something; } ????

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