doni49 Posted January 2, 2016 Share Posted January 2, 2016 I'm reading through some older threads on the forum -- I find that reading other people's issues and the answers they receive is a great education in itself -- and saw some code in a reply posted by Barand that I don't understand. Here's a link to the post in question http://forums.phpfreaks.com/topic/299309-cumulative-sum-in-mysql-view-calculating-running-profitloss/?do=findComment&comment=1525829 The code in question: JOIN (SELECT @cum:=0) init @cum:=@cum+profit as cum_profit I get that the @ symbol indicates a global variable. But what is the := for? And is this "init" being used similar to a for loop? Quote Link to comment Share on other sites More sharing options...
requinix Posted January 2, 2016 Share Posted January 2, 2016 A single equals sign means comparison; @cum=0 would be saying "is @cum equal to 0". Colon+equals does assignment and will set @cum to 0 in the first part and then add profit in the second part. And yes, the init part is working like the init part in a for loop. for ($cum = 0; ; $cum = $cum + $profit) {You could do the assignment in a separate query beforehand SELECT 0 INTO @cumwhich would be like $cum = 0; for (; ; $cum = $cum + $profit) { Quote Link to comment Share on other sites More sharing options...
benanamen Posted January 2, 2016 Share Posted January 2, 2016 Just one thing that wasn't mentioned, it is called a user-defined variable in case you or someone else wants to look it up. Quote Link to comment Share on other sites More sharing options...
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