Union does a distinct on all results. UNION ALL will avoid that. Regards, Gavin Towey
-----Original Message----- From: chen.1...@gmail.com [mailto:chen.1...@gmail.com] On Behalf Of chen jia Sent: Monday, April 05, 2010 11:07 AM To: mysql@lists.mysql.com Subject: Slow Union Statement Hi there, I run simple statement like this: create table c select * from a union select * from b; where table a has 90,402,534 rows, and table b has 33,358,725 rows. Both tables have the same three variables. It's taken a long time, more than half an hour now. How do I make it faster? Best, Jia -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=gto...@ffn.com This message contains confidential information and is intended only for the individual named. If you are not the named addressee, you are notified that reviewing, disseminating, disclosing, copying or distributing this e-mail is strictly prohibited. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. E-mail transmission cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. The sender therefore does not accept liability for any loss or damage caused by viruses or errors or omissions in the contents of this message, which arise as a result of e-mail transmission. [FriendFinder Networks, Inc., 220 Humbolt court, Sunnyvale, CA 94089, USA, FriendFinder.com -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
