A quick way to ORDER all IDs randomly in MySQL

I need to assign random IDs to a table. Thus, I create a mapping table as CREATE TABLE t2 ( ID int(11) unsigned NOT NULL AUTO_INCREMENT, SourceID int(11) unsigned NOT NULL, UNIQUE INDEX(SourceID), PRIMARY KEY(ID) ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COLLATE utf8_general_ci KEY_BLOCK_SIZE=1 and then added the IDs from the main table t1 as INSERT IGNORE INTO t2 (SourceID) SELECT ID FROM t1 ORDER BY RAND() For example, imagine t1 is the test results of the students, and we do not want to reveal the student ID (t1.ID) to reviewers (for an anonymous review). Then, we show each record with a new ID stored in t2. SELECT t2.ID AS NewID, t1.results FROM t1 JOIN t2 ON t1.ID=t2.SourceID The problem is t1 is tens of millions of rows and RAND() is very very slow. I do not need a perfect RAND() here; just assigning new IDs (somehow randomly arranged). Can you think of an approach to do query faster?