yiisoft/yii2 — pull request #2124 by iworker (2014-01-23 04:53:40+00:00)
Title: Update QueryBuilder.php

Change using of implode to convert array of queries to union to array_reduce. Result of this changing is that code feel difference between two selects that connects with UNION and two selects that connects with UNION ALL.

This PR must be connected with this : https://github.com/yiisoft/yii2/pull/2123