diff --git a/phpBB/includes/db/dbal.php b/phpBB/includes/db/dbal.php
index cf54d455f7..bf0dc15fad 100644
--- a/phpBB/includes/db/dbal.php
+++ b/phpBB/includes/db/dbal.php
@@ -283,6 +283,23 @@ class dbal
 		return $this->_sql_like_expression('LIKE \'' . $this->sql_escape($expression) . '\'');
 	}
 
+	/**
+	* Build a conditional SQL query
+	*
+	* @param	string	$condition		The condition which must be true, to use action_true rather then action_else
+	* @param	string	$action_true	SQL statement that is used, if the condition is true
+	* @param	string	$action_else	SQL statement that is used, if the condition is false, optional
+	* @return	string			CASE expression including the condition and statements
+	*/
+	function sql_conditional($condition, $action_true, $action_false = false)
+	{
+		$sql_condition = 'CASE WHEN ' . $condition;
+		$sql_condition .= ' THEN ' . $action_true;
+		$sql_condition .= ($action_false !== false) ? ' ELSE ' . $action_false : '';
+		$sql_condition .= ' END';
+		return $sql_condition;
+	}
+
 	/**
 	* Returns whether results of a query need to be buffered to run a transaction while iterating over them.
 	*