Hi! Could someone please explain to me why the second query below is faster then the first query? The only difference between the two is that ext_doc_id's value is quoted. Index and column information follow and the table being queried contains approximately 3.5 million rows.
Thanks! --Dave EXPLAIN SELECT doc_id FROM documents WHERE interface='tasklist' AND ext_doc_id=412625; +-----------+------+---------------+------+---------+-------+-------+-------------+ | table | type | possible_keys | key | key_len | ref | rows | Extra | +-----------+------+---------------+------+---------+-------+-------+-------------+ | documents | ref | idx7 | idx7 | 30 | const | 94761 | Using where | +-----------+------+---------------+------+---------+-------+-------+-------------+ 1 row in set (0.03 sec) EXPLAIN SELECT doc_id FROM documents WHERE interface='tasklist' AND ext_doc_id='412625'; +-----------+------+---------------+------+---------+-------------+------+-------------+ | table | type | possible_keys | key | key_len | ref | rows | Extra | +-----------+------+---------------+------+---------+-------------+------+-------------+ | documents | ref | idx7 | idx7 | 60 | const,const | 3 | Using where | +-----------+------+---------------+------+---------+-------------+------+-------------+ 1 row in set (0.00 sec) +---------------------+---------------------+------+-----+---------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------------+---------------------+------+-----+---------------------+----------------+ | doc_id | int(10) unsigned | | PRI | NULL | auto_increment | | revision_number | smallint(6) | | | 0 | | | user_id | int(10) unsigned | | MUL | 0 | | | origin_id | int(10) unsigned | | MUL | 0 | | | pat_id | int(10) unsigned | | MUL | 0 | | | doc_type | char(10) | | MUL | | | | storage_type | int(10) unsigned | | | 0 | | | storage_id | bigint(20) unsigned | | | 0 | | | volume_id | char(1) | YES | | NULL | | | filename | char(255) | YES | | NULL | | | service_location | char(10) | YES | | NULL | | | origin_date | datetime | | | 0000-00-00 00:00:00 | | | enter_date | datetime | | MUL | 0000-00-00 00:00:00 | | | revision_date | datetime | | | 0000-00-00 00:00:00 | | | service_date | datetime | | | 0000-00-00 00:00:00 | | | approx_service_date | tinyint(1) unsigned | | | 0 | | | review_date | datetime | | | 0000-00-00 00:00:00 | | | review_user_id | int(11) | | | 0 | | | ext_doc_id | char(30) | | | | | | interface | char(30) | | MUL | | | +---------------------+---------------------+------+-----+---------------------+----------------+ 20 rows in set (0.00 sec) mysql> show index from documents; +-----------+------------+----------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+ | Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | +-----------+------------+----------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+ | documents | 0 | PRIMARY | 1 | doc_id | A | 3566754 | NULL | NULL | | BTREE | | | documents | 1 | idx2 | 1 | pat_id | A | 89168 | NULL | NULL | | BTREE | | | documents | 1 | idx2 | 2 | service_date | A | 1188918 | NULL | NULL | | BTREE | | | documents | 1 | idx3 | 1 | pat_id | A | 89168 | NULL | NULL | | BTREE | | | documents | 1 | idx3 | 2 | doc_type | A | 891688 | NULL | NULL | | BTREE | | | documents | 1 | idx3 | 3 | service_date | A | 1783377 | NULL | NULL | | BTREE | | | documents | 1 | idx4 | 1 | user_id | A | 223 | NULL | NULL | | BTREE | | | documents | 1 | idx4 | 2 | revision_date | A | 1783377 | NULL | NULL | | BTREE | | | documents | 1 | idx5 | 1 | origin_id | A | 289 | NULL | NULL | | BTREE | | | documents | 1 | idx5 | 2 | origin_date | A | 1783377 | NULL | NULL | | BTREE | | | documents | 1 | idx7 | 1 | interface | A | 10 | NULL | NULL | | BTREE | | | documents | 1 | idx7 | 2 | ext_doc_id | A | 63692 | NULL | NULL | | BTREE | | | documents | 1 | idx8 | 1 | doc_type | A | 255 | NULL | NULL | | BTREE | | | documents | 1 | idx8 | 2 | storage_type | A | 488 | NULL | NULL | | BTREE | | | documents | 1 | idx9 | 1 | enter_date | A | 1783377 | NULL | NULL | | BTREE | | +-----------+------------+----------+--------------+---------------+-----------+-------------+----------+--------+------+------------+---------+ David W. Juntgen Medical Informatics Engineering Inc. Phone: 260.459.6270 Fax : 260.459.6271 -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
