I'm using mysql 3.23.49 on Linux redhat dedicated server.
Here is my query : mysql> show index from MyTable; ############################ Table : MyTable Non_unique : 0 Key_name : PRIMARY Seq_in_index : 1 Column_name : Field0 Collation : A Cardinality : NULL Sub_part : NULL Packed : NULL Comment : NULL ############################# Table : MyTable Non_unique : 0 Key_name : Index1 Seq_in_index : 1 Column_name : Field3 Collation : A Cardinality : NULL Sub_part : NULL Packed : NULL Comment : NULL Table : MyTable Non_unique : 0 Key_name : Index1 Seq_in_index : 2 Column_name : Field0 Collation : A Cardinality : NULL Sub_part : NULL Packed : NULL Comment : NULL ############################# Table : MyTable Non_unique : 0 Key_name : questions Seq_in_index : 1 Column_name : Field2 Collation : A Cardinality : NULL Sub_part : NULL Packed : NULL Comment : NULL Table : MyTable Non_unique : 0 Key_name : questions Seq_in_index : 2 Column_name : Field3 Collation : A Cardinality : NULL Sub_part : NULL Packed : NULL Comment : NULL Table : MyTable Non_unique : 0 Key_name : questions Seq_in_index : 3 Column_name : Field4 Collation : A Cardinality : NULL Sub_part : NULL Packed : NULL Comment : NULL MyTable info : Field0 : int(10) unsigned primary key Field1 : int(10) unsigned Field2 : int(10) unsigned Field3 : int(10) unsigned Field4 : datetime Null: Yes default 0000-00-00 00:00:00 ( but this field don't have null values ) Field5 : varchar(50); mysql> explain SELECT * FROM Forums WHERE Field2=5020 AND Field3=0 ORDER BY Field4 DESC LIMIT 0,20; ************** table : MyTable type : ref possible_keys : Index1,questions key : questions key_len : 1 ref : const,const rows : 390 Extra : where used; Using filesort 1 row in set (0.00 sec) We can see that index questions which have Fields 2, 3 and 4 isn't use for the order by. Why ? Thanks in advance David --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <mysql-unsubscribe-##L=##[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
